Across:
8 Frank (HONEST), Henry (H-) and Oscar (-O-) from the tree house (-NEST) (HONEST),
9 It rarely (it rarely = LITERARY) worried (= anagram indicator) academic (academic/learned = LITERARY),
10 Jack in (jack in/pack in = STOP) part of Sevastopol (part of ‘sevaSTOPol’ = STOP),
11 Sick and tired (CHEESED OFF) of what’s said to the photographers (CHEESE-) and director (-D) not getting on (getting OFF) (CHEESED OFF),
12 Learnt (learnt = RENTAL) builder (= anagram indicator) provided temporary accommodation (RENTAL),
14 Resist the temptation (RESTRAIN) to show off (= anagram indicator) trainers (trainers = RESTRAIN),
15 Typically heard creating a scene (BACKGROUND MUSIC) in land (GROUND) behind (= position indicator) yard (BACK) with swing (swing MUSIC) (BACKGROUND MUSIC),
18 Likes to share (FLATMATE) with novice (learner = -L-) consumed by stout (F- AT-) and Bud? (-MATE) (FLATMATE),
20 Uses up the budget (SPENDS) for writer (-PEN-) and director (-D-) in Titanic, for example (RMS Titanic steamship = S-S) (SPENDS),
22 State (NORTH KOREA) of Ulster? (NORTH) A divided country! (north / south KOREA) (NORTH KOREA),
24 One of The Greens (LIME green) in Muslim establishment (in “musLIM Establishment” = LIME),
25 Terrible (= anagram indicator) curse (curse = CRU-ES) going around Down (down = -SAD-) (CRUSADES) in the religious wars (CRUSADES),
26 Upsets (= reversal indicator) shirty types (tops = -SPOT) working on paper (editor = ed = DE-) (DESPOT) for tyrant (DESPOT).
Down:
1 Foams out of false bottom (‘foams’ out of ‘false bottom’ = lebtto = BOTTLE) in plastic container (BOTTLE),
2 Operated without rota (‘operated’ without ‘rota’ = peed = DEEP) – how profound is that? (DEEP),
3 There’s no pleasing purist (STICKLER) nun (Sr = S-R) with a frog in her throat (-TICKLE-) (STICKLER),
4 Remove organ from lounge bar (remove ‘organ’ from ‘lounge bar’ = lueb = BLUE) for The Navy (BLUE),
5 Assist (assist = STASIS) Whip (= anagram indictor) in period of inactivity (STASIS).
6 Wall Street figure (trader = TRADE R-) is away (-OUT-) getting drugs (-E) (TRADE ROUTE) for the traffickers (TRADE ROUTE),
7 Airmen (-RAF-) taking tantrum (-FIT-) caught by soldier (GI = G-I) (GRAFFITI) writing on the wall (GRAFFITI),
13 Steal (TAKE) from Count (tot = TO T-) and invite (-ASK) (TAKE TO TASK) reprimand (TAKE TO TASK),
14 By the way (ROUTE), it’s at the end of 6 down (at the end of ‘trade route’ = ROUTE),
16 444 (ALL FOURS) offering 7 Up? (game ‘Seven Up’ / ‘High-Low-Jack’ also called ALL FOURS),
17 Parts company (DISBANDS) for final period (final ‘period’ = -D-) in Sinbad’s (Sinbad’s = DISBAN-S) novel (= anagram indicator) (DISBANDS),
19 First-class (AI-) miner (‘miner’ = ‘minor’ = -KID-) says (= homophone indicator) nothing (-O) (AIKIDO) as a form of self-defence (AIKIDO),
21 Academic (D-ON) welcomes a (-A-) manuscript (-MS-) (DAMSON) by Deep Purple (DAMSON),
23 Relax (REST) – it’s part of the Welfare State (it’s part by the “welfaRE STate” = REST)
24 Young woman (LASS) raised (= reversal indicator) in Thessaloniki (in ‘TheSSALoniki’ = ssal = LASS).