Across:
8 Get to grips with (MASTER) meandering (= anagram indicator) stream (stream = MASTER),
9 Make a point of asking (QUESTION) inquiry (QUESTION),
10 Taught initially (‘taught’ initially = T-) in school (-RAY) (TRAY) by one of those from the canteen (TRAY),
11 Short (k) honest (‘frank’ without ‘k’ = FRAN-) soldier (-GI-) hears (= homophone indicator) Sting (“pain” = “pane” = -PANE) (FRANGIPANE) and Cream (FRANGIPANE),
12 Hits (hits = ISTH-) bad (= anagram indicator) road (-MI) (ISTHMI) in Panama with others (ISTHMI),
14 Aircraft (JET-) is not (is not = -TISON) (JETTISON) flying (= anagram indicator) – get rid of it (JETTISON),
15 The best posers (QUESTION MASTERS) with 9 across (‘question’ = QUESTION) and 8 across (‘master’ = MASTER-) at school (-S) (QUESTION MASTERS),
18 One (I-) barber’s pole (-SIGN-) in Ulster (-N-I-) is a (-A) (INSIGNIA) badge of honour (INSIGNIA),
20 It’s going to be tight (NARROW) in new (N-) Dart (dart/missile = -ARROW) (NARROW),
22 Caught (C-) it (-IT-) in variety (variety = -REATIV-Y) (CREATIVITY) show – Off (show-off = anagram indicator) With Imagination (CREATIVITY),
24 Wharf (QUAY) trader missing for quarter day? (‘trader’ missing for/from ‘quarter day’ = quay = QUAY),
25 Determined (HELL-BENT) darling of Paris (Helen of Troy married Paris = HEL- -EN-) admits knocking back (= reversal indicator) lawyer (BL = -L-B-) from Troy (-T) (HELL-BENT),
26 Navy (N-) is unsuccessful (failed), leaderless (f) (‘failed‘ without ‘f’ = -AILED) (NAILED) and gets hammered (NAILED).
Down:
1 Bill (law = WAL-) goes back (= reversal indicator) to cut (t) reddish-brown (‘rust’ without ‘t’ = -RUS) (WALRUS) type of facial hair (WALRUS moustache),
2 Stick around (STAY) for St Patrick’s Day bands (‘St Patrick’s Day’ bands = STAY),
3 The writing is on the wall (GRAFFITI) and it can be cutting (graft = GRAF-T-) about endless (x) drug taking (‘fix’ without ‘x’ = -FI-) at institute (-I) (GRAFFITI),
4 Reacquaints with missing cretins (‘reacquaints’ with missing ‘cretins’ = aqua= AQUA) – the shady type (AQUA colour),
5 Ken is out on a week night (‘Ken’ is out on a ‘week night’ = weight = WEIGHT) – it’ll tell on the scales (WEIGHT),
6 Relative (STEPSISTER) raises (= reversal indicator) cats and dogs (pets = STEP-) in the nunnery (-SISTER) (STEPSISTER),
7 Torrential rain (DOWNPOUR) in county (Co DOWN-) with river (-PO-) by old city (-UR) (DOWNPOUR),
13 Friendly welcome (HOSPITABLE) to bishop (-B-) in medical centre (HOSPITA-L-) from last Pope (last ‘Pope’ = -E) (HOSPITABLE),
14 Journalists (NUJ = JUN-) upset (= reversal indicator) at the first (‘the’ first = -T-) American (-A) (JUNTA) military government (JUNTA),
16 Unsettled (UNNERVED) by organisation (UN-) for Denver (Denver = -NERVED) conversion (= anagram indicator) (UNNERVED),
17 Woman (ANN-) loses the head (t) toying (toying) (‘toying’ without ‘t’ = -OYING) (ANNOYING) with irritating type (ANNOYING),
19 Tennis shoe missing? Then (‘tennis shoe’ missing ‘then’ = nissoe = NOISES) rackets! (NOISES),
21 Talks (ORATES) by old (O-) judges (-RATES) (ORATES),
23 A bit (IOTA) of canal coming out of Catalonia (‘canal’ coming out of ‘Catalonia’ = taoi = IOTA),
24 Grill (QUIZ) perhaps opened by one of those in 15 across (QUIZ opened by one of the ‘question masters’).