3933 Lay___ Out by Zero

Gregson certainly enjoyed completing this clever puzzle. The letters absent from wordplay gave the quotation - "_____ is a geographical expression" (Metternich), missing the word Italy which was indicated by the title. When entering words in the grid extra letters gave the names of seven Italian cities, which had to be replaced by large dots. In grid order: Milan (sawmill/cyanogenesis), Turin (ring out/statute), Venice (ventpipes/delice), Genoa (stroamed/cyanogenesis), Florence (florescence/pretence), Rome (acid drop/same), Naples (unapplied/plessors).The continuous line of 19 straight lines drew a map of Italy with the seven cities lying in their correct situations. The main difficulty would be in joining the dots to form the correct outline.

Letters not entered are shown by square brackets. Letters absent from wordplay in thematic clues are in bold type.

*44a National independence in prospect but not inevitable, legally speaking (4)
NISI N (national) + I (independence)
2a Twitchy county councillor died aboard vessel (8)
SACCADIC CC + d (died) in SAIC
19d Reptile contributing regularly to the Sun (4)
TEGU odd letters of ThEsUn
*2d Special decoration for person: it shortly could be law (7)
STA[TU]TE]S (special ) + tatu + t (shortened form of it)
23d Making a circle around the moon, perhaps mistakenly inhale nitrogen (9)
*21d Water-carrier entered violently, dropping Ecstasy (10, two words)
*46a Omniscience sees nothing in a flower (8)
PANSOPHY O (nothing) in pansy
15a Blank note covered in old filth (6)
IGNORE N in gore
26a Learning to lake spades inside garden boundary? It's blooming time (11)
[FLORE]SCENCE LORE (learning) + S (spades) in FENCE
*39a Stable stone by lake (5)
STALL ST (stone) + L
28a Disciples in abundance (5)
SONSE Disciples is SONS
13a Urge island sticks to seaweed (6)
OREXIS ORE (seaweed) + IS (island)
5d Mere ten-centilitre bottles a con, perhaps (8)
*33d Highly charged with rows of blue and white shields (6)
VERREY Highly = very
14a Woodcutter? One with William's trouble (7)
*42a Become fatigued, lacking energy for a month (5)
TISRI tir(e)
1d Snappy clothes I provide at back streets (10, two words)
TSOTSI SUIT I SUIT (provide) after TS TS (ST rev.)
17d Received a letter back describing talk with no fluency (7, three words)
UM AND AH Had a mu (rev.)

8 Beat back tailless beast (4)
MALL Llam(a) rev.
12 Remain anonymous in insalubrious surroundings (4)
STAY A in STY anonymous is abbreviated to A as in Alcoholics Anonymous.
16 Clearly sound note, following drummer (7, two words)
[RIN]G OUT Ringo (Starr) + UT
18 Outlets for little boy caught in turbulent events (9)
[VEN]T-PIPES PIP in anag. Events
22 Strong one in left-leaning protest took steps (7)
STR[OA]MED STR (strong) + A in DEMO (rev.)
24 Sow lettuce, initially in Egypt (3)
ELT L in ET (Egypt)
29 River lover concealing source (3)
EAU (B)eau
30 Imitate cricket, with vital energy leading to runs (5)
CHIRR chi +RR (runs)
31 Sweet abandon, hooked on drug (8, two words)
ACID D[RO]P drop (abandon) after acid(drug)
34 Hit croquet ball, but not with end of mallet (3)
ICE (T)ice
36 Pure peace organisation apparently gave false impression? (9)
UN[AP]PLIED UN + app + lied
37 Foot has end of toe behind throwing-line, following the rule (7)
TROCHEE T (the) R (rule) + oche + E (end of toe)
40 Shanty town in preferred city (6)
FAVELA fave + LA
43 Approached artist's chamber (6)
CAMERA came + RA
45 Navy aircraftsman's term of abuse (4)
NERK N (navy) + erk

3 Blue book about old poison production process (12)
CY[AN]O[GEN]ESIS (Blue) CYAN + O (old) + Genesis (Book of Bible)
4 Saddle horse with cropped tail (3)
COL Col(t)
6 Tasty treat of French insects (6)
DEL[ICE] de + lice
7 Soldier Corps goes up in smoke (3)
C (corps) + GI rev.
9 Fallout shelter run in American security operation? (8)
ALOPECIA LOPE (run) in A (American) CIA Nice hidden definition!
10 See about Latin rogue (5)
LOREL Lo + re + L
11 Throw fish back in Edmund's river (3)
LEE eel rev.
20 Pierre's ready to eat mushroom in principle (7)
PRECEPT cep in prêt
25 Harsh treatment of earl in leg-side fielding position (8)
ONCEOVER E (earl) in ON (leg-side) COVER
27 Unvaried modesty has husband leaving (4)
SA[ME] s(h)ame
29 Education, for example, raised incisiveness (4)
EDGE Ed + e.g. rev.
32 Hammers crowd changes direction, with standing room only up at the end (8)
P[LES]SORS Press (change R to L(eft)) SRO rev.
35 Scots claim Conservative Party (5)
CRAVE C + rave
38 E number used by producer of bone meal bread? (4)
ETEN E + ten ref. Giant in Jack of the Beanstalk -" I'll grind his bones to make my bread"
40 Name of upwardly-mobile old fool (3)
FON n(ame) of reversed
41 Wash cloth wrap (3)
LAP 3 meanings
42 Way pipe reverses (3)
TAO oat rev.