Across:
8 It's arbitrary (RANDOM) in capital (monetary unit of South Africa = RAND-) of Morocco, for starters ('Of Morocco' for starters = -OM) (RANDOM),
9 Last horse (last ‘horsE’ = E-), cross (-X-) on maiden (maiden) run (= anagram indicator) (maiden = -AMINED) (EXAMINED), checked by vet (EXAMINED),
10 Finally settle (finally ‘settlE’ = -E) after (= position indicator) brief (r) muddle (‘blur’ without ‘r’ = BLU-) (BLUE) in Navy (navy BLUE),
11 Those working on the farm (HORSES-) with gardening equipment (-HOES) (HORSESHOES) – the lucky things (HORSESHOES),
12 Cuts (butcher’s cuts = STEAKS) type of wood (-TEAK-) going into ship (SS = S-S) (STEAKS),
14 This will definitely stop you going out for the night (INSOMNIA), as with this you won’t have what’s in 6 down (won’t have ‘nightmares’ with INSOMNIA),
15 Go to pieces (SHATTER-) in (-IN-) Government (-G) following (= position indicator) heart (heart) problem (= anagram indicator) (heart = EARTH) (EARTH-SHATTERING) – it’s like being hit by an asteroid (EARTH-SHATTERING),
18 Those controlling the apps (PROGRAMS) from buggies (prams = P-RAMS) around mid-afternoon (mid ‘afteRnoon’ = -R-), love (-O-) golf (-G-) (PROGRAMS),
20 What you might get from 22 across (get LESSON from ‘art teacher’) as a potential warning (LESSON),
22 Employed in a classy drawing room (ART TEACHER) by one informing the masters of tomorrow in a crafty way (ART TEACHER),
24 Extremes of Security Council (extremes of ‘SEcurity councIL’ = seil) bringing up (= reveres indicator) (seil = LIES) statements that aren’t true (LIES),
25 Made a difference to (AFFECTED) Bill (bill/ad = A-D) holding party (Fianna Fáil = -FF-) for top executives (top ‘Executives’ = -E-), etc. (etc), retiring (= reverse indicator) (etc = -CTE-) (AFFECTED),
26 Heartless (heartless = remove centre = ‘n’) old jailer (‘turNkey’ without ‘n’ = TURKEY) produces the usual for Christmas (TURKEY).
Down:
1 Is missing from Bastille ('is' missing from 'Bastille' = batlle = BALLET) in the flames of Paris, for instance (Boris Asafyev's 'The Flames of Paris' = BALLET),
2 Latinos from delegations (‘Latinos’ from ‘delegations’ = deeg = EDGE) on the brink of something (on the EDGE),
3 Importance (EMPHASIS) of hams, pies (hams, pies), bananas (= anagram indicator) (hams, pies = EMPHASIS),
4 Buck (DEER) raised (= reverse indicator) in Rush (reed) (reed = DEER),
5 Educators missing our (‘educators’ missing ‘our’ = edcats = CADETS) officers in training (CADETS),
6 Bad experiences (NIGHTMARES) – many people suffered these after they’ve retired (NIGHTMARES),
7 Ned Eliot (Ned Eliot) played (= anagram indicator) (Ned Eliot = DELETION) with Erasure? (DELETION),
13 Singer in the choir (ALTO-) is backing (= reverse indicator), for example (e.g. = -GE-), tenor (-T-) and that woman (-HER) (ALTOGETHER) in Toto (in toto = ALTOGETHER),
14 Friend in Paris (French ‘friend’ = ami) reviews (= reverse indicator) (ami = IMA-) manuscript (ms = -MS) (IMAMS) by church leaders (IMAMS),
16 One of those perhaps planning to take off (planning to take-off = AIRCRAFT) broadcast (AIR-) by one of those overseas (-CRAFT) (AIRCRAFT),
17 Turn a blind eye (TOLERATE) to (TO-) the French (‘the’ French = -LE-) judge (-RATE) (TOLERATE),
19 Transforms (ADAPTS) fresh (= anagram indicator) tapas (tapas = A-APTS) around Dublin (-D-) (ADAPTS),
21 It’s exposed (OPENED) by old (O-) writer (-PEN-) employed by the paper (editor = -ED) (OPENED),
23 Hitting one’s stride going around (‘HItting one’s striDE’ going around = HIDE) in leather (HIDE),
24 Muck around (LARK) on the banks to lay the groundwork (on the banks to ‘LAy the groundwoRK’ = LARK).