Quick Cryptic 425 by Orpheus

A puzzle that I thought was at the tougher end of the scale, with some less than commonplace vocabulary.

The crossword can be found here if the usual channels are unavailable: http://feeds.thetimes.co.uk/timescrossword/20151026/10374/

Definitions are underlined.

Across
1	Peel's first deed, producing treaty (4)
	PACT - P (Peel's first, i.e. the first letter of "Peel") + ACT (deed)
3	Steala Kandinsky painting, for example? (8)
	ABSTRACT - double definition, the second referring to the Russian artist Wassily Kandinsky, who (per WIkipedia) is "credited with painting one of the first purely abstract works"
9	Rhode Island's one and only savoury dish? (7)
	RISSOLE - RIS (Rhode Island's) + SOLE (one and only). Chambers: "A fried ball or cake of minced seasoned meat or fish coated in breadcrumbs"
10	Rodent has change of heart, seeing big creature with horns (5)
	MOOSE - MOuSE (Rodent) but wth the middle letter U (heart) changed to an O. Interestingly, this set of checkers cropped up in the first preliminary of the Times Crossword Championships just over a week ago, though with the answer MYOPE (and obviously a very different clue) - it took me ages to get MOOSE out of my mind at the time.
11	Picked up sound made by group of animals, say (4)
	HEARD - homophone (say) of HERD (group of animals)
12	Abduct child, then take forty winks (6)
	KIDNAP - KID (child) + NAP (take forty winks)
14	Way Essex town's character is an aid to progress (8-5)
	STEPPING-STONE - ST (Way, i.e. street) + EPPINGS (Essex town's) + TONE (character)
16	Energetic person's awful Monday! (6)
	DYNAMO - anagram (awful) of MONDAY
19	Daggers supplied by old boy and priest (5)
	OBELI - OB (old boy) + ELI (priest). An obelus (singular) is one of these: †
22	In maturity the Italian is nimble (5)
	AGILE - IL (the Italian, i.e. an Italian word for "the") inside AGE (maturity)
23	Recently clothed in bright colour - as mother and daughter are (7)
	RELATED - LATE (Recently) inside (clothed in) RED (bright colour)
24	Regretful writer, one given shelter (8)
	PENITENT - PEN (writer) + I (one) + TENT (shelter)
25	Musical atmosphere met by Handel at first (4)
	HAIR - H (Handel at first, i.e. the first letter of "Handel") + AIR (atmosphere). The rival of Evita for the title of Crosswordland's most popular musical.

Down
1	Buyleverage (8)
	PURCHASE - double definition
2	Conspirator involved in Guernica's capture? (5)
	CASCA - hidden(involved) in GuerniCA'S CApture. One of Caesar's assassins.
4	Chicken thieves may do it, and also if caught in the act! (5,4,1,3)
	BREAK INTO A RUN - double definition, the first literal and referencing a chicken run
5	Mousy chap a girl's thrown over (5)
	TIMID - TIM (chap) + reversal (thrown over) of DI (a girl)
6	Fruit provided by a very old accountant at party (7)
	AVOCADO - A + V (very) + O (old) + CA (accountant) + DO (party)
7	Arduous march leaders of the Royal Engineers finally undertook (4)
	TREK - TRE (leaders of the Royal Engineers, i.e. the first letters of "the Royal Engineers) + K (finally undertook, i.e. the last letter of "undertook")
8	Delay in violent robbery? (4-2)
	HOLD-UP - double definition
13	Display greater ferocity to confuse (8)
	BEWILDER - BE WILDER (Display greater ferocity)
15	Blissfully happy Welsh girl supporting Cambs city (7)
	ELYSIAN - SIAN (Welsh girl) after (supporting) ELY (Cambs city). Probably most often encountered in the phrase "Elysian fields", which itself is probably most often encountered as the French "Champs-Elysees".
16	Damagesbooty (6)
	SPOILS - double definition
18	Expert in a small section of store (5)
	ADEPT - A + DEPT (small section of store, i.e. a shortened version of the word "department"). My second Quick cryptic in a row with this answer.
20	Exceptionallywide, for example (5)
	EXTRA - double definition, the second referring to an example of an extra in cricket
21	Possesses penny to get hinged plate (4)
	HASP - HAS (Possesses) + P (penny)