Across:
8 Account (AC-) by a (-A-) group of spies (-CIA) (ACACIA) – one is a plant (ACACIA),
9 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),
10 Arab ruler (EMIR) takes part in rebellious (= reverse indicator) experiment (in ‘expeRIMEnt’ = rime = EMIR)
11 For a time, one looks up to this (CLOCK TOWER) college (C-) to secure (-LOCK) from local Yank (local ‘yank’ = pull = TOW-) in hospital facility (-ER) (CLOCK TOWER),
12 Maverick (MISFIT) Frenchman (Monsieur = M-) leading the pack (1ST = -IS-T) around Formula One (-FI-) (MISFIT),
14 Took off (STRIPPED) in small (S-) tour (-TRIP-) with heads on performance enhancing drugs (heads on ‘Performance Enhancing Drugs’ = -PED) (STRIPPED),
15 Vocal (= homophone indicator) confrontational encounter (‘duel’ = ‘DUAL”) with coach (CARRIAGE-) on track (-WAY) (DUAL CARRIAGEWAY) is over a couple of lanes and could go in either direction (DUAL CARRIAGEWAY),
18 With great skill (ADROITLY) plays around with (= anagram indicator) idolatry (idolatry = ADROITLY),
20 Electric shock from leads (‘Electric Shock’ from leads = ES-) indicates (-SAYS) (ESSAYS) criticisms of the students (ESSAYS),
22 Panorama (PROSPECT-) editor (-ED) (PROSPECTED) made investigations into the mining industry (PROSPECTED),
24 Roulette ball limits (‘ROulette baLL’ limits = ROLL) circular movement (ROLL),
25 Stock (PEDIGREE) of jeans (jeans), in a manner of speaking (= homophone indicator) (‘jeans’ = ‘genes’ = PEDIGREE),
26 Unstable (= anagram indicator) lab set (lab set = TABLES) used by the mathematicians (TABLES).
Down:
1 Is (is = S-I) backtracking (= reverse indicator) over David, for one (Camp David = -CAMP-), (SCAMPI) producing something fishy (SCAMPI),
2 Top, sweater (top ‘Sweater’ = S-) and mini (-CAR) (SCAR) makes a lasting impression (SCAR),
3 Personal assistant (P-A) gets to grips with knife (lancet) starting off (l) (‘lancet’ without ‘l’ = -ANCET-) to take bone (-T- bone) (PANCETTA) out of meat from Italy (PANCETTA),
4 Muse (CLIO = Greek and Roman muse of history) about (= reverse indicator) contents of topsoil collected (contents of ‘topsOIL Collected’ = oilc = CLIO),
5 A person of note outside (BUSKER) producing the numbers on the street (BUSKER),
6 Sources of zest (LEMON PEELS) in solemn (solemn) adaptation (= anagram indicator) (solemn = LEMON -S) about Trim (PEEL-) (LEMON PEELS),
7 Separatist movement (ETA = ET -A) around revolutionary (= anagram indicator) Crete (Crete = CETER-) (ET CETERA) and the rest (ET CETERA),
13 Don’s (dons = FELLOWS-) trendy joint (-HIP) (FELLOWSHIP) is a club promising camaraderie (FELLOWSHIP),
14 Hold your horses dismissing household? (‘hold your horses’ dismissing ‘household’ = yrors = SORRY) I beg your pardon! (SORRY),
16 Is not given enough (UNDERFED) by Hungary (Hungary) state (= homophone indicator) (‘Hungary’ = ‘hungry’ = UNDERFED),
17 One cadet (one cadet) fishing (= anagram indicator) (one cadet = ANECDOTE) for an account that’s unreliable (ANECDOTE),
19 Holy Father doesn’t get half (‘Holy Father’ doesn’t get ‘half’ = oyther = THEORY) the speculation (THEORY),
21 Cried (YELLED) for Yankee (Y-) women’s magazine (-ELLE-) opening debate? (opening ‘Debate’ = -D) (YELLED),
23 Some Vermeer technique (some ‘vermEER Technique’ = eert) revolutionary (= reverse indicator) (eert = TREE) and noticeable presumably in Klimt’s Birch Forest (TREE),
24 Wedding celebration (40th wedding anniversary = RUBY wedding) in one of the ports (RUBY port).