Across:
8 Let out of bell tower (‘let’ out of ‘bell tower’ = blower = BOWLER) to go on ahead (BOWLER hat goes on a head),
9 Foreign (= anagram indicator) troop (troop = PROTO-) officer (Colonel = -COL) (PROTOCOL) produced rules of engagement (PROTOCOL),
10 Trip (SLIP) around the sides of slave ship (around the sides of ‘SLave shIP’ = SLIP),
11 Quote (TENDER-) from travel agent perhaps (-FOOT) (TENDERFOOT) to American rookie (TENDERFOOT),
12 Nutcase (PSYCHO) begins post seminary year (starts ‘Post Seminary Year’ = PSY-) at church (-CH-) order (-O) (PSYCHO),
14 Duck (-O-) in premium (premium = EMP-RIUM) butchers (= anagram indicator) (EMPORIUM) – a large store (EMPORIUM),
15 Proves Freud’s theory (SLIP OF THE TONGUE) in 10 across (‘slip’ = SLIP) on old French (Old French = OF) article (THE) by 26 across (‘tongue’ = TONGUE) (SLIP OF THE TONGUE),
18 Sounds harsh (TUNELESS) for most of (a) the fish (‘tuna’ without ‘a’ = TUN-) at English (-E-) takeaway (-LESS) (TUNELESS),
20 Special (= anagram indicator) cheer (cheer = RE-ECH-) for duck? (-O) (RE-ECHO) Give me that again! (RE-ECHO),
22 Conscious (DELIBERATE) of India’s second largest city- (‘Delhi’ = ‘deli’ = DELI-) -state (= homophone indicator) getting to read the Riot Act (read the riot act = -BERATE) (DELIBERATE),
24 One of The Greens (LIME green) in Muslim establishment (in “MusLIM Establishment” = LIME),
25 Pupil leaves splinter group (‘pupil’ leaves ‘splinter group’ = sntergro = STRONGER) in better condition (STRONGER),
26 What the butcher is selling (TONGUE) with boar from Baton Rouge (‘boar’ from ‘Baton Rouge’ = tnouge = TONGUE).
Down:
1 Nothing (O-) short of (d) odd (‘odd’ without ‘d’ = -OD-) for the French (the = -LES) (OODLES) in large numbers (OODLES),
2 Take sow away from cowslip (‘sow’ away from ‘cowslip’ = clip = CLIP) to prune it (CLIP),
3 Whiskey (W-) sour (-OFF) arrives finally (= positional indicator) – service (-RITE) (WRITE-OFF) isn’t one to remember (WRITE-OFF),
4 Old (O-) writer (-PEN) (OPEN) is undone (OPEN),
5 Work out (TONE UP) why she leaves penthouse? (‘she’ leaves ‘penthouse’ = pentou = TONE UP),
6 Conor (CON-) Ward (-ER-) taken in by local dealer of stolen goods (fence = -F-ENCE) (CONFERENCE) in forum (CONFERENCE),
7 Polish (hone) didn’t finish (e) (‘hone’ without ‘e’ = HON-) old (-O-) trainee (learner = -L-) university (University of Limerick = -UL-), upsetting principal (‘Upsetting’ principal = -U) (HONOLULU) in American city (HONOLULU),
13 Is this what plagiarists are expected to do (COPY EDITOR) working for the advertising company? (COPY EDITOR),
14 The (the = ETH-) boss (= anagram indicator) is old (-O-) school (-S) (ETHOS) with cultural values (ETHOS),
16 Cut (l) tree (‘Laurel’ without ‘l’ = LAURE-) tops at the entrance (tops ‘At The Entrance’ = -ATE) (LAUREATE) by court appointment in the poetic sense (LAUREATE),
17 Ribs (TORMENTS) and bone (T- bone) from mysterious (= anagram indicator) monster (monster = -ORMENTS) (TORMENTS),
19 It will come out (EMERGE) as English (E-) join forces (-MERGE) (EMERGE),
21 The funny side (HUMOUR) to buzz (HUM-) from old (-O-), old city (-UR) (HUMOUR),
23 Old city (ACRE / Israel) in the Armagnac region (in the ‘ArmagnAC REgion’ = ACRE),
24 Left (L-) for the journalist (-INK) (LINK) to make the connection (LINK).