Quite a tricky challenge from Monk this morning.
A most enjoyable puzzle, with a lovely nina. Some tricky words and parsing, but all completely fair of course. Many thanks to Monk! And happy hoaxing to all on this day.

ACROSS
6. Reckless behaviour of handler is so upsetting (13)
FOOLHARDINESS
(OF HANDLER IS SO)* (*upsetting)
10. Each rounded turbine blade catches minute component of Spitfire? (9)
AEROMOTOR
EA< (each, <rounded) + ROTOR (turbine blade) catches MO (minute)
11. Business plugs revolutionary top-notch clubbing Mecca (5)
IBIZA
BIZ (business) plugs AI< (top-notch, <revolutionary)
12. For and against hosting extremely chatty star (7)
PROCYON
(PRO (for) and ON (against)) hosting C[hatt]Y (extremely)
13. Staff centre on standby initially absorbing pressure after unknown number sacked (7)
SCEPTRE
CE[n]TRE on S[tandby] (initially); absorbing P (pressure) after N (unknown number) sacked
14. Struggling, ultimately for years, to get best value above all else? (3,5,5,2)
SET GREAT STORE BY
([fo]R (ultimately) + YEARS TO GET BEST)* (*struggling)
18. Off and on, groups betray philosopher (7)
RUSSELL
[g]R[o]U[p]S (off and on) + SELL (betray)
21. “Un-American” newspaper item about European network (7)
RETICLE
[a]RTICLE (newspaper item, un-American, i.e. no A) about E (European)
23. Quietly follow discussion on society (5)
STALK
TALK (discussion) on S (society)
24. Specialist food store with cheerful drug causing frenzy (9)
DELIRIANT
DELI (specialist food store) with RIANT (cheerful)
25. Act shrewdly? Old boy fobs one off (2,7,4)
BE NOBODY’S FOOL
(OLD BOY FOBS ONE)* (*off)
DOWN
1. Cross over job part of the way in? (8)
DOORPOST
ROOD< (cross, <over) + POST (job)
2. Sadly, mucilage covering left and central parts of false eye (6)
GLUMLY
(GUM (mucilage) covering L (left)) and [fa]L[se] [e]Y[e] (central parts of)
3. Decorates bar up in Swansea after walls repeatedly stripped (6)
ADORNS
ROD< (bar, <up) in [sw]ANS[ea] (after walls repeatedly stripped)
The ‘walls’ of the word ‘Swansea’ are the outer letters, and we remove (strip) these repeatedly, so more than once
4. Some rampant bore hit naïve, ignoble protagonist (8)
ANTIHERO
[b]ORE HIT NA[ive]< (some, <rampant)
5. Help animal point away from front (6)
ASSIST
Cryptic definition
“ASS 1st”
7. Receiver’s advance payment not available after noon (7)
ANTENNA
ANTE (advance payment) + (NA (not available) after N (noon))
8. In the morning, sap rising in soft split on tall plant (6,5)
PAMPAS GRASS
(AM (in the morning) + SAP< (<rising)) in P (soft) + GRASS (split)
9. Peter and Betty swimming round lake with small means of protection? (6,5)
SAFETY BELTS
SAFE (peter) and (BETTY* (*swimming) around L (lake)) with S (small)
15. Bond running free, overturning defeat (4,4)
REEF KNOT
FREE* (*running) + TONK< (defeat, <overturning)
16. Keenly, exhausted hiker fills potty (7)
SHRILLY
H[ike]R (exhausted) fills SILLY (potty)
17. Vegetable that’s key with almost all spicy wraps (8)
ESCHALOT
ESC (key) with (AL[l] (almost); HOT (spicy) wraps)
19. Disturbed Poles catching fish (6)
SHAKEN
S, N (poles, South, North) catching HAKE (fish)
20. Left upland country, rising around university town in Shropshire (6)
LUDLOW
(L (left) + WOLD< (upland country, <rising)) around U (university)
22. Frugality essentially buried in most of the Financial Times (6)
THRIFT
[bu]RI[ed] (essentially) in (most the TH[e] + FT (Financial Times))
New words for me today: RIANT, TONK, and ESCHALOT. All good, thank you Monk and Oriel
10a. I think this is AE (each rounded) ROTOR (turbine [blade?]) catches MO.
19d. I had SKATES (disturbed STAKES), but SHAKEN is better, agreed.
Thanks both!
Thanks Olof @2 – yes, I had not accounted for the E in 10a. I’ll amend this. Thank you!
Thanks Monk and Oriel
5dn: I had ASS (animal) + [g]IST (point away from front)
I knew I’d missed something
Thanks all and Paul