Across:
8 Representing Ulster (-NI-) in school (fish = FI-SH) (FINISH) cap (cap/conclude = FINISH),
9 A (A-) banned body builder (-STEROID) (ASTEROID) with a heavenly body (ASTEROID),
10 Lends a hand (AIDS) to headless (r) busts? (raids) (‘raids’ without ‘r’ = AIDS),
11 Confuses (= anagram indicator) it in survey (it in survey = UNIVERSITY) with one of those places where The Don makes a living (UNIVERSITY),
12 Dad’s lover (MUM-) found at address in Salem (in Salem, India, a polite form of address = -BAI) (MUMBAI), an Indian city? (MUMBAI),
14 They report what’s happening (MEDIA-) in front of (= position indicator) The Hill (-TOR) (MEDIATOR) to referee (MEDIATOR),
15 Celebrate (MARK THE OCCASION) with 24 across (‘mark’ = MARK) and most of (m) them (‘them’ without ‘m’ = THE) at get-together (OCCASION) (MARK THE OCCASION),
18 It’s ironic, in the Smiley sense (ironic WRY- smile), one of those on the bottle (-NECK-) is finished (‘iS’ finished = -S) (WRYNECKS) producing families of woodpeckers? (WRYNECKS),
20 Not the first (‘Not’ the first = N-) to back doctor (back ‘doctoR’ = -R-) in practice (use = -U-SE-) taking direction (South = -S) (NURSES) from sisters (NURSES),
22 To help out (CONTRIBUTE) criminal (CON-) with expression of praise in statement (-TRIBUTE) (CONTRIBUTE),
24 Frenchman (M-) on flood defence (-ARK) (MARK) in old capital (old capital/money = German MARK),
25 Next of kin (RELATION) in Oriental (Oriental) novel (= anagram indicator) (Oriental = RELATION),
26 Surface (EMERGE) of estuary leading (‘Estuary’ leading = E-) to pool (-MERGE) (EMERGE).
Down:
1 Marry (mix) Trim (x) (‘mix’ without ‘x’ = MI-) gossip (-LIE-) from university (-U) (MILIEU) with cultural surroundings (MILIEU),
2 Works on the plot weeding out (DIGS) extremes of director’s feelings (extremes of ‘DIrectors feelinGS’ = DIGS),
3 Describes a spirit at Halloween (GHOULISH) in Lough (Lough = GHOUL-) Mask (= anagram indicator) taking head off (f) trout (fish) (‘fish’ without ‘f’ = -ISH) (GHOULISH),
4 Soldier (-GI) following (= position indicator) leaders masquerading as (leaders ‘Masquerading As’ = MA-) (MAGI) sorcerers (MAGI),
5 Turn up (ATTEND) for a (A-) race (Tourist Trophy race = -TT-) meeting on purpose (goal/aim = -END) (ATTEND),
6 Begs forgiveness (sinner/TRESPASSER) for what Alsatian in the security business is looking for (TRESPASSER),
7 Skilful type (VIRTUOSO) is against (versus = V-) riotous (riotous) movement (= anagram indicator) (riotous = -IRTUOSO) (VIRTUOSO),
13 Endless (d) sinful (‘bad’ without ‘d’ = BA-) gratin (gratin) dish (= anagram indicator) (gratin = -ING TRA-) consumed in Kerry (-K-Y) (BAKING TRAY) comes out of the oven (BAKING TRAY),
14 Spirits (MOODS) to scrounge from consumer goods? (‘scrounge’ from ‘consumer goods’ = omods = MOODS),
16 Renewable energy from a farm perhaps (AIR POWER) is used by flighty types as part of a campaign (AIR POWER part of a war),
17 Scam (CON-) caught (-C-) by a pair of writers? (Ed +Ed = -EDED) (CONCEDED) In the past I would have given you that! (CONCEDED),
19 So-and-so abandons accordionists (‘so-and-so’ abandons ‘accordionists’ = ccriit = CRITIC) for a job on the paper (CRITIC),
21 Make someone see red (ENRAGE) with a green (a green) salad (= anagram indicator) (a green = ENRAGE),
23 Runs (runs) out (= anagram indicator) (runs = URNS) for The Ashes (URNS),
24 Namesake dismisses NASA (‘namesake’ dismisses ‘NASA’ = meke = MEEK) as spineless (MEEK).