Across:
8 Psychiatrist won't take physic ('psychiatrist' dismisses 'physic' = atrist = ARTIST) from one drawing on their imagination (ARTIST),
9 Popular (IN-) outlet (-VENT-) in the centre of Cork (centre of ‘cORk’ = -OR) (INVENTOR) produced by architect (INVENTOR),
10 First class (AI-) detective (Detective Sergeant = -DS) (AIDS) is a good Samaritan (AIDS),
11 They’ll get you thinking (BRAIN CELLS) what the headcase is presumably holding (BRAIN) for those in The Joy (CELLS) (BRAIN CELLS),
12 Nutcase (PSYCHO) begins post seminary year (starts ‘Post Seminary Year’ = PSY-) at church (-CH-) order (-O) (PSYCHO),
14 European (CROATIAN) actor in a (actor in a) play (= anagram indicator) (actor in a = CROATIAN),
15 Sack (FIRE) popular (IN) individuals (ONE’S) associated with food processor (BELLY) (FIRE IN ONE’S BELLY) with raging enthusiasm (FIRE IN ONE’S BELLY),
18 Sounds like (= homophone indicator) some nights (some ‘nights’ = ‘knights’ = CHESSMEN) you’ll find them in the pawnshop presumably? (CHESSMEN),
20 Character (LETTER) risked a removal from Kildare Street (‘risked a’ removal from ‘Kildare Street’ = ltreet = LETTER),
22 Sweet cocktails (fruit cocktail = FRUIT SALAD) for most of those in 1 down (most ‘fruits’ = FRUIT) at the start of 17 down (start of ‘salad bar’ = SALAD) (FRUIT SALAD),
24 A guilty pleasure (VICE) of some taken in by retiring (= reverse indicator) Argentine civilians (some taken in by ‘argentinE CIVilians’ = eciv = VICE),
25 Beastly types (STOCK-) needing no introduction (m) produced (‘made’ without ‘m’ = -ADE) (STOCKADE) something that acts as a defence against attack (STOCKADE),
26 Check out (ASSESS) ship (-SS-) in wild (= anagram indicator) seas (seas = A-ESS) (ASSESS).
Down:
1 Bananas (FRUITS) or tomatoes? (FRUITS),
2 Calls from bridge (calls from game of bridge = BIDS) going around Bissagos Islands (going around ‘BIssagos islanDS’ = BIDS),
3 Uncompromising (STUBBORN) Top Secret (top ‘Secret’ = S-) Review (= reverse indicator) nevertheless (but = -TUB-) delivered (-BORN) (STUBBORN),
4 Bit of improvisation (bit of ‘improVISAtion’ = VISA) required for getting into some countries (VISA),
5 In spite of that (EVEN SO), first lady (EVE-) joins symphony (National Symphony Orchestra/ NSO = -N SO) (EVEN SO),
6 It could be risky (INVESTMENT) up (reverse indicator) north (NI = IN-) for 24 down (‘vest’ = -VEST-) on worker’s (-MEN-) square (-T square) (INVESTMENT),
7 For checking who is there (ROLL CALL) for the presents? (presents / absents on ROLL CALL),
13 One of those in 18 across (CHESSPIECE is one of the ‘chessmen’) is a bishop (CHESSPIECE),
14 Could start (‘Could’ start = C-) soon, according to the linesman (-ANON = soon according to the linesman/poet) (CANON), in principle (principle/rule = CANON),
16 Is left (INHERITS) by cool (IN-) guy (-HE-) arising from (= reverse indicator) mix-up (stir = -RITS) (INHERITS),
17 Young man (-LAD) taking note (music note B-) in German state (Saar = SA- -AR) (SALAD BAR) where Dieter (dieter) gets his lunch? (SALAD BAR),
19 Lose an item (MISLAY) in a slimy (a slimy) bake (= anagram indicator) (a slimy = MISLAY),
21 Old partner (EX-) is (-IS-) in church? (Church of England = CE = -C-E) (EXCISE) Remove! (EXCISE),
23 Vegetable (LEEK) found in river (River LEE-) close to Murmansk (close to ‘murmansK’ = -K) (LEEK),
24 Sides with venture capitalist (sides with ‘VEnture capitaliST’ = VEST) taking the shirt off your back exposing this (VEST).