Across:
8 Ill-humoured (MOROSE) beast (MO-OSE) swallows ram’s head (‘Rams’ head = -R-) (MOROSE),
9 Is painstakingly careful (THOROUGH) protecting Rose (thorn) briefly (n) (‘thorn’ without ‘n’ = THOR-) heading off (r) around the course (‘rough’ without ‘r’ = - OUGH) (THOROUGH),
10 Part of backlog repudiated (part of ‘backlOG REpudiated’ = OGRE) by pantomime villain (OGRE),
11 Commissioning (APPOINTING) new (= anagram indicator) painting (painting = AP-INTING) drawing in river (-PO-) (APPOINTING),
12 High Courts extracted this (‘high courts’ without ‘this’ = hgcour = GROUCH) from a fault-finder (GROUCH),
14 Introduces 15 across (introduces ‘Mandarin Chinese’ = MANDARIN) produced by mogul (MANDARIN),
15 Chap (MAN-) is not completely (g) brave (‘daring’ without “g” = -DARIN) opening 22 across (opening ‘Chinese red’ = CHINESE) (MANDARIN CHINESE), in a manner of speaking (MANDARIN CHINESE),
18 Used to carry a torch for (OLD FLAME) one of those presumably at last Olympics (OLD FLAME),
20 More stout (LARGER) for redhead (‘Red’ head = -R-) consumed by drink (LA-GER) (LARGER),
22 Oriental wine presumably (CHINESE RED) produced by Mao (CHINESE RED),
24 Dislikes chucking out disk (‘dislikes’ chucking out ‘disk’ = lies = LIES) of made-up stories (LIES),
25 Answer (A-) from head of industry (head of ‘industry’ = -I-) in environmentally friendly (green = -GREE-N-) Government (-G-) (AGREEING) giving one’s approval (AGREEING),
26 Cathy’s (Cathy’s) all at sea (= anagram indicator) (Cathys = YACHTS) in pleasure crafts (YACHTS).
Down:
1 Takes up space (LODGER) in someone else’s house (LODGER),
2 The benefit (DOLE) of reviewing (= reversal indicator) what’s in Nickelodeons (what’s in ‘NickELODeons’ = elod = DOLE),
3 Symbolic type (METAPHOR) of team (team) playing (= anagram indicator) (team = META-) with power (-P-) and fair amount of (half of) horror (half of ‘HORror’ = -HOR) (METAPHOR),
4 Falls over (= reversal indicator) cats and dogs (pets = STEP) outside the front door (STEP),
5 Far cry from confirmatory (‘far cry’ from ‘confirmatory’ = onimto = MOTION) proposal (MOTION),
6 Coaches the boxers (DOG TRAINER) and keeps them on a tight leash until they recognise who’s in charge (DOG TRAINER),
7 Overturned (= reversal indicator), for example (e.g. = -GE-), submerged in case (in case) prepared (= anagram indicator) (in case = A-NCIES) (AGENCIES) by Governmental groups (AGENCIES),
13 Tried to justify (-DEFENDED) opening (= position indicator) organisation (UN-) (UNDEFENDED) that’s not supported (UNDEFENDED),
14 Who goes off Chow Mein (‘who’ goes off ‘chow mein’ = cmein = MINCE) produced with shredded steak? (MINCE),
16 Everyone (ALL) starts to harden (starts ‘To Harden’ = TH-) self-image (self-image = ego = -E GO) (ALL THE GO) in Vogue (ALL THE GO),
17 Christmas Day, St Stephen’s Day (HOLIDAYS) and the rest (rest on HOLIDAYS),
19 Sounds like (= homophone indicator) an auction (‘a sale’ = ‘ASSAIL’) in Rush (rush/charge = ASSAIL),
21 Lets off steam (-VENTS) after (= position indicator) engineering (E-) (EVENTS) big social gatherings (EVENTS),
23 Fury (RAGE) internalised by suffragette (internalised by ‘suffRAGEtte’ = RAGE),
24 Moths from Stockholm (‘moths’ from ‘Stockholm’ = ckol = LOCK) may have been picked? (pick a lock = LOCK).