I am not sure why, but I found this very challenging. Peto’s clues seem perfectly fine, so I don’t know what the disconnect was.

| ACROSS | ||
| 1 | RACKET |
Pandemonium in game briefly (6)
|
| RACKET[S] (game) minus last letter (briefly), evidently a forerunner of squash | ||
| 4 | STUCCO |
Plaster head of saint, mysterious on reflection, student ignored (6)
|
| First letter of (head of) S[AINT] + OCCU[L]T (mysterious) reversed (on reflection) and minus (ignored) L (student) | ||
| 8 | UNEARTH |
Dig up a French article on cunning Hungarian leader (7)
|
| UNE (a French article) + ART (cunning) + first letter of (leader [of]) H[UNGARIAN] | ||
| 9 | NARRATE |
Tell fled heading west at speed (7)
|
| RAN (fled) reversed (heading west) + RATE (speed) | ||
| 11 | BORDERLINE |
Course of action following marches only just acceptable (10)
|
| BORDER (marches) + LINE (course of action) | ||
| 12 | AGED |
Consented to get rid of soldiers advanced in years (4)
|
| AG[RE]ED (consented) minus (to get rid of) RE (soldiers) | ||
| 13 | SPAWN |
Make Native American give up drugs after last of warnings (5)
|
| Last [letter] of [WARNING]S + PAWN[EE] (Native American) minus (give up) {E + E} (drugs) | ||
| 14 | COCKSURE |
Arrogant nonsense to take legal action against boxing trainer ultimately (8)
|
| COCK (nonsense) + {SUE (to take legal action against) around (boxing) last letter of (ultimately) [TRAINE]R} | ||
| 16 | START OFF |
Initiate rule about books framed by teachers in school (5,3)
|
| {R (rule) + OT (books) reversed (about)} inside (framed by) STAFF (teachers in school) | ||
| 18 | EXERT |
Use effectively with skilful removal of pressure (5)
|
| EX[P]ERT (skilful) minus (removal of) P (pressure) | ||
| 20 | BARD |
Prevented from speaking with poet (4)
|
| Homophone of (speaking) BARRED (prevented from) | ||
| 21 | MERCANTILE |
Commercial enterprise initially involved in spurious rent claim (10)
|
| First letter of (initially) E[NTERPRISE] inside (involved in) anagram of (spurious) {RENT CLAIM} | ||
| 23 | PIQUANT |
Stimulating for oddly prim fashion designer perhaps (7)
|
| Odd letters of (oddly) P[R]I[M] + [Mary] QUANT (fashion designer perhaps) | ||
| 24 | SILENCE |
The rest is for Hamlet to put a stop to (7)
|
| Double definition, the first referring to Hamlet’s dying words: “The rest is silence.” | ||
| 25 | NOTICE |
Time allowed for preparation of literary review (6)
|
| Double definition | ||
| 26 | FREELY |
Not under the control of another female dance company finally (6)
|
| F (female) + REEL (dance) + last letter of (finally) [COMPAN]Y | ||
| DOWN | ||
| 1 | RUN TO |
Be sufficient for trip to get Manx cat (3,2)
|
| RUN (trip) + TO[M] (cat) minus last letter, i.e., minus his tail, thus “Manx” | ||
| 2 | CHALDEA |
Ancient region’s prince died in church near Assyria’s capital (7)
|
| {HAL (prince) + D (died)} inside (in) CE (church) + first letter of (capital [of]) A[SSYRIA] | ||
| 3 | ENTER INTO |
Be interested in record set by piebald horse needing no introduction (5,4)
|
| ENTER (record, i.e., read as a verb) + [P]INTO (piebald horse) minus first letter (needing no introduction) | ||
| 5 | TEASE |
Support holding captive as bait (5)
|
| TEE (support) around (holding captive) AS | ||
| 6 | CARCASS |
Around the beginning of April replacing one ship’s framework (7)
|
| C[I]RCA (around) substituting (replacing) first letter of (beginning of) A[PRIL] for I (one) + SS (ship) | ||
| 7 | ON THE TROT |
Troubled throne to face battles essentially one after the other (2,3,4)
|
| Anagram of (troubled) {THRONE TO} + middle letter of (essentially) [BAT]T[LES] | ||
| 10 | PITCHFORK |
Lie mostly over hankering at first for tosser seen on farm (9)
|
| PORK[Y] (lie) minus last letter (mostly) around (over) {ITCH (hankering) + first letter of (at first) F[OR]} | ||
| 13 | SITUATION |
Combination of circumstances making yours truly stressed about living in Swiss town (9)
|
| {I (yours truly) + TAUT (stressed) inverted (about)} inside (living in) SION (Swiss town) | ||
| 15 | CHEVALIER |
Gallant in good spirits catches sound daughter missed (9)
|
| CHEER (good spirits) around (catches) VALI[D] (sound) minus (missed) D (daughter) | ||
| 17 | REDOUBT |
Retrieve data from computer reportedly found in temporary fortification (7)
|
| Taking some liberty with the pronunciation: Homophone of (reportedly) READ OUT (retrieve data from computer) | ||
| 19 | EXTREME |
Far from moderate constituents of Rex meet (7)
|
| I think this parses as: Anagram of (moderate [i.e., as a verb] constituents of) REX MEET | ||
| 21 | MANIC |
Frantically busy FBI agent not good in charge (5)
|
| [G-]MAN (FBI agent) minus (not) G (good) + I/C (in charge) | ||
| 22 | LUCKY |
Attended by good fortune gutsy Penny fled (5)
|
| [P]LUCKY (gutsy) minus (fled) P (penny), with a capitalization misdirection | ||
Thanks both. Agree was fiddly rather than impossible.
I found it challenging too, Cineraria, and only three quarters finished. My “Huh?” list grew rather long, in many instances due to deficiencies in my knowledge. I should have known — I seldom seem to get on Peto’s wavelength.