3966: Mercury's Whereabouts by Dysart

Dysart gave us a lovely puzzle with some tough clues that made solving difficult. The puzzle's theme was a novel and extra words gave us THE PAST IS A FOREIGN COUNTRY. These are the opening words of the prologue to the Go-Between by LP Hartley. Down clues had to be fitted in the grid and the redundant words had to go between the entries. These extra words were GO or synonyms of GO and in the clue order a – m they corresponded with the columns in the grid. Finally solvers had to highlight the novel's three principal characters MARIAN, LEO and TED, appropriately positioned with Leo in the middle. The title refers to finding Leo, the messenger, and WHEREABOUTS is an example of the Go-Between entries, BOUT in WHEREAS.
Extra letters in wordplay and redundant words are shown in square brackets.

ACROSS
1 Going back in time, one has first taste of Chilean wine (6)
ASCENT A (one) ’S (has) C(hile) + [T]ENT (wine)
7 Parts of crab, or lobster possibly, I nearly chucked in pool, once (6)
PLEONS PLES[H] (pool) containing ON(E)
14 Gets off clothes, ignoring cold, going around naked (7)
DEBARKS DECKS (clothes) less C containing BAR[E]
15 Inclined to give gratuity lodging in "Milton's Rest" (5)
ATILT TI[P] in ALT
16 Fruit and vegetable -- no time to preserve (4)
PEPO PE[A] + POT (preserve) less T (time)
18 A love's abandoned after onset of fit of depression (6)
FOVEAL F(it) + anag. A LOVE’(S)
19 Where one learns to make a lasting impression (4)
TECH T’ (to) + E[T]CH
20 Good (chaste?) girl's missing good time (3)
AGE AGG[I]E (Agnes is explained in Chambers as meaning chaste) less G (good) + T (time)
21 This poet twists hearts ... (5)
PLATH PLAT[S] + H (ref. Sylvia Plath)
22 ... like this old lover's grave (6)
SOLEMN SO (like this) + LEM[A]N
24 Troublemaker's opener: "Go and get lost." Offensive moment? (3)
TET T (first letter of TROUBLEMAKER) + [F]ET (old word meaning FETCH, here LOST means obsolete)
25 "Cash settlement. Hey, save" (5)
PAISA PA (settlement) + I[O] + SA’ (obs. contraction of SAVE)
26 Lord deprived of power tries working - most unnatural (7)
EERIEST (P)EER (less P (power) + anag. T[R]IES
27 Placate riotous boxing group (4)
TRIO Hidden PLACAT[E] RIOTOUS
28 Bones and front of skull found in rocks near Lyme Regis perhaps (4)
LIAS [I]LIA (bones) + S(kull)
29 Bishop leaves bribe; moderation's followed by extremes of luxury. Dreadful!
6)
UNHOLY BUN[G] (bribe) less B (bishop) + HO (moderation) + L(uxur)Y
30 Europeans from north-east, fast talkers (extremely) (5)
LETTS LE[N]T (fast) + T(alker)S
31 Movement having distinct energy? Energy's dissipated (5)
LARGO [C]LEAR (distinct) + GO (energy) less E (energy)
32 Cut beginning of Psycho? That's a challenge (3)
VIE (M)[O]VIE less first letter
33 Being castrated, the ultimate cut, gets the highest note (4)
NETE NE[U]TER less last letter
34 Rushing sailors charge after Manx cat? (7)
TORRENT TO(M) (here Dysart wants us to understand Manx cat as a cat without a tail or last letter) + R[N] + RENT
35 A short path leading to large lake (5)
ONEGA (2nd largest lake in Europe) ONE (A) + GA[T](E)
36 Being sick - messy, could be messier (6)
EMESIS Anag. MESSIE[R]
37 Backward fellow (not all there) having to wait around for totty in Central Park? (6, two words)
RUG RAT Here TOTTY means TODDLER. TARR(Y)  containing GU[Y] (all reversed)
DOWN
(a) Old region's oddball – [spell]binding Indian levitating (9)
CLIMATURE CURE² containing TAMIL (reversed)
(b) Seven out of the south [go] east, breaking up part of a ring perhaps (9)
PLEONASTE PLEON(S) (answer to clue SEVEN) less S + anag. EAST
(c) Reinforcements blown up in lane – [life] lost (10)
TENAILLONS Anag. IN LANE LOST
(d) Aged "Sir" had lost [zest] for teaching (6)
LORING LORDING (SIR archaic) less ’D (had)
(e) ["Vim"] does possibly just over half of cleaning, saving time (4)
DEER (does possibly) DETER(GENT) less T
(f) Certify growth of [PEP] investment? Yes, according to report; no, on inspection (8)
NOTARISE sounds like NOTE A RISE
(g) Materialistic person to make good [deal] importing the first pieces of licensed ivory (9)
EARTHLING EARN + G(ood) containing TH’ (the) + L(icensed) + I(vory)
(h) Elizabeth succeeded after introduction to kick [turn] was unsuccessful in winter resort (8)
KLOSTERS K(ick) + LOST (was unsuccessful) + ER (Queen Elizabeth) + S (succeeded)
(i) Animal's violent [bout] with heartless tamer (8, two words)
WHITE RAT Anag. WITH TA(M)ER
(j) Agents have [shot] at soldiers inside offices of old governor (9)
SATRAPIES AT RA (Royal Artillery) in SPIES
(k) [Move] young bird, lying half hidden (8)
NESTLING 2 meanings
(l)[ Kick] a chap standing up half sober - it's a form of greeting (7)
NAMASTE A MAN (reversed) + STE(ADY)
(m) Swallowing drug before I try to begin, I make my way across country (9)
ORIENTEER E (that drug again) in OR I ENTER