Across:
8 Recalls (= reverse indicator) first class (AI = -IA) heroin (-H-) hidden by young man (lad = DA-L-) (DAHLIA) in Mexican plant (DAHLIA),
9 Yearly exam (PHYSICAL exam) will discover if you have 7 down, for instance (PHYSICAL will locate ‘backache’),
10 Jones’ partner (DOW- Jones) is opening nursery (opening ‘Nursery’ = -N) (DOWN) in Ulster (DOWN),
11 The writer is responsible for this movement (DOWNSTROKE) in 10 across (‘down’ = DOWN-) and 21 down (‘stroke’ = -STROKE) (DOWNSTROKE),
12 Lost (L-) desire (-ITCH-) for one (-I) (LITCHI) Chinese fruit (LITCHI),
14 Jazz solo (lick = LI-CK) contains merit (merit) – missing the last (t) (‘merit’ without ‘t’ = -MERI-) (LIMERICK) five lines that’s poetic (LIMERICK),
15 Primitive (UNSOPHISTICATED) organisation (UN-) linked to Cosmopolitan (-SOPHISTICATED) (UNSOPHISTICATED),
18 Importance (EMPHASIS) of hams, pies (hams, pies), bananas (= anagram indicator) (hams pies = EMPHASIS),
20 Fraud (MISUSE) by mysterious missing Tory (‘mysterious’ missing ‘Tory’ = mseius = MISUSE),
22 Horse (GG = G-G-) running around Wales (Wales) oddly (= anagram indicator) (Wales = LASWE-) heads for Ireland, Ayr, Newbury (heads for Ireland, Ayr, Newbury = -IAN) and Ascot? (‘Ascot’ = ‘a scot’ = GLASWEGIAN),
24 An encore called for (MORE!) those characters in auditorium or exhibition (those characters in ‘auditoriuM OR Exhibition’ = MORE),
25 Devised (= anagram indicator) epic sale? (epic sale = ESPECIAL) That’s unusual! (unusual = ESPECIAL),
26 Is indispensable to a suit (SLACKS) with skinhead (‘Skin’ head = S-) and it is missing (is missing = -LACKS) (SLACKS).
Down:
1 One (-I) taking shifts in the factory (rotas) all arising (= reverse all indicator) (rotas = SATOR-) (SATORI) out of what the Buddhists say is enlightening (SATORI),
2 Dynasty (CLAN) from The Eternal City (from the ‘eterNAL City’ = nalc) going all the way back (= reversal indicator) (nalc = CLAN),
3 Ocean liner (SAND-) which (which) lacks height (h)? (‘which’ without ‘h’ = -WICH) (SANDWICH) The one that’s toasted and named after The Lord! (toasted SANDWICH + Earl of SANDWICH),
4 Spout out (SPEW) the extremes of Spiro Agnew (the extremes of ‘SPiro agnEW’ = SPEW),
5 Mouthy type (G-UM) admits turning (= reversal indicator) secret agent (spy = -YPS-) (GYPSUM) involved in the construction of The Wall (GYPSUM),
6 They know where there are stacks (library stacks) of Dubliners (LIBRARIANS / James Joyce’s “Dubliners”) employed in a book depository (LIBRARIANS),
7 It creates a strain after doing all the heavy lifting (BACKACHE) giving support (BACK-) to a (-A-) revolutionary (-CHE) (BACKACHE),
13 Online clip (CLOTHES PEG on clothes line) of gear (CLOTHES) for going to gym (PE-) ahead of game (ahead of ‘Game’ = -G) (CLOTHES PEG),
14 Flips over (flips/leans over = LISTS) composer (Liszt) on the radio (= homophone indicator) (‘Liszt’ = ‘list’ = LIST-) associated with first symphony (first ‘Symphony’ = -S) (LISTS),
16 Call (NAME-) to Takeaway (take away = -LESS) (NAMELESS) – the one that’s not easy to describe (NAMELESS),
17 One (I-) pair of Frenchmen (Messieurs = -MM-) take drugs (U-SE) going around Ulster (-NI-) (IMMUNISE) to protect from infection (IMMUNISE),
19 Duff (= anagram indicator), since (since = SCENI-) going to college (-C) (SCENIC) presumably, has a view (SCENIC),
21 Butterfly, for example (butterfly STROKE in swimming), found in small (S-) wild (= anagram indicator) trek (trek = -TR-KE) around Oxford (-O-) (STROKE),
23 Inactive (IDLE) summits of Isla de los Estados (summits of ‘Isla De Los Estados’ = IDLE),
24 Sound like (= homophone indicator) cheese-pairing (cheese-paring = MEAN) that’s not at all nice (MEAN).