4029 Office Block by Duck
This was a pleasing puzzle from the prolific setter Duck, with a religious theme timed for Easter weekend.

Extra letters in wordplay spelt out THE CANONICAL HOURS, which can also be called “offices”, thereby explaining the title. These are set hours for prayers said throughout the day. Other clues led to answers entered with a single misprint in the grid. After these had been resolved, a series of diagonals could be seen to spell out LAUDS, PRIME, TERCE, SEXT, NONE, VESPERS and COMPLINE, the names of prayers in their correct order, and these had to be highlighted in the grid.

The preamble alluded to MATINS, which did not appear in the grid, but this was not needed for submission.

Extra letters, and grid entries, are indicated by [].

1 Seizes power, entering field? (6)
CLASPS [CRASPS] P (power) inside CLASS (field)
7 Northerners continue to keep very quiet (5)
LAPPS[T] LAST (continue) containing PP (very quiet)
12 Monkey eating hard nuts in tree (7)
MADR[H]ONA MONA (Monkey) containing ADRH (anagram of HARD)
13 Wise fellow in a shop in the Metro Centre? (6)
The Metro Centre being one of the UK’s biggest shopping centres, located in Gateshead
14 Having crossed track, see rock god (6)
VARUNA [IARUNA] RUN (track) inside V (Vatican City ie the Holy See) + AA (rock)
16 What gets read at home? Various mags taking ages, not half! (8, two words)
GAS METER [GAS METDR] GASM (anagram of MAGS) + ETER (first half of ETERNITY ie ages)
17 Glass she carved is given to Holly? (5)
S[C]ILEX SC (she sculpted) + ILEX (Holly)
18 Variable scale in which one's found lines (5)
CEILS[A] CELSA (anagram of SCALE) containing I (one)
19 Bowler, good person brought in as who's not yet had a match (8)
SPIN[N]STER SPINNER (Bowler) containing ST (Saint ie good person)
24 Ray has one urge that's perverse - to be a rat (8)
RE[O]NEGUER  RE (Ray) + ONE + GUER (anagram of URGE)
27 Violet needs money coming in to entertain partners at table (5)
PANSY [PANRY] PAY (money coming in) containing NS (North + South ie partners at a bridge table)
29 Primitive life forms in asteroid I analysed! (5)
OIDIA [OIDIR] Hidden in asterOID I Analysed
30 Jock's coat is dumped in garden pot (8)
PLA[N]ISTER IS inside PLANTER (garden pot)
31 One slowing down, needing older company, having eye trouble (6)
IRITIC[I] I (One) + RIT (ritardando ie slowing down) + ICI (former PLC)
ICL is another possibility for “older company” but gives the wrong letter in the hidden message
32 An absence of good drink, but drink there is (6)
NOGGIN [NOGEIN] NO (An absence of) + G (good) + GIN (drink)
34 Like a housewife of old, giving number supply of food (7)
NOTABLE [NOTOBLE] NO (number) + TABLE (supply of food)
35 Once set on, retreating moggy gets to blunder about (5)
TARRE[C] CAT (moggy) containing ERR (blunder), all reversed
36 Approved reform to restrict drug (6)
AMENED [AMENEE] AMEND (reform) containing E (drug)
1 If your electrical device fails, you may do this puzzle (7)
CONFUSE [CONFSSE] CON FUSE (ie study fuse carefully)
2 Like Scottish kipper - coming initially from bay, that is (6)
REEKIE [REEKIP] C (first letter of COMING) removed from CREEK (bay), + IE (that is)
3 Foreign soul spiritless, wasting time (3)
AME [AMS] TAME (spiritless), less T (time)
4 Fabric had to be wrapped in net (6)
SATEE[A]N ATE (had) inside SEAN (net)
5 Barber's uplifting constituent melodies (5)
STRAP [SRRAP] PARTS (constituent melodies), reversed
6 Maybe give juice to put old desire that's gone into fellows (7)
MO[L]ISTEN O (old) + LIST (desire) inside MEN (fellows)
8 A worry about Eastern demon (6)
AFREET [AAREET] A + FRET (worry) containing E (Eastern)
9 Flatness of parking space (9)
10 23 held up in Lancashire borough (6)
PENDLE[H] PEN (writer, ie the answer to 23 Down) + HELD reversed
11 Hunted one is one escaping copper (5)
SNARK [SNARS] IS less I (one), + NARK (copper)
The reference is to The Hunting of the Snark, by Lewis Carroll
15 Person transferring property works out rationale (9)
20 Get tense over property - if the deceased wasn't this? (7)
TESTATE [TESTCTE] T (tense)  + ESTATE (property)
21 Position horse in harness with two pieces the wrong way round (7)
ARR[O]ANGE ROAN (horse) inside GEAR (harness), with two halves reversed
The more obvious ANG for NAG (horse) confused Gregson for a while
22 In veneration novice faces a temptation endlessly (6)
LATRIA [LALRIA] L (learner ie novice) + A + TRIA(L) (temptation, less last letter)
23 Scottish lawyer - someone to redress wrong, we hear (6)
25 One fiddle needed for son to render old tune (6)
G[U]INGLE GU (fiddle) for S (son) in SINGLE (one)
26 Rarely able to see and no longer lively, is staying in (6)
VISIVE [EISIVE] VIVE (old word for lively) containing IS
27 Plant with a spade that's left in shed (5)
SPLIT [PPLIT] SPIT (Plant with a spade) containing L (left)
28 Fluttering orange sail (5)
GENOA[R] Anagram of ORANGE
33 Noticed a poet's decline (3)
[S]EEN Two definitions (one containing extra letter)