Some pleasing material here from this inventive setter.
Solving time: 25 mins
* = anagram
ACROSS
1 COAT OF ARMS (A from Ascot)* Did not see this till late on. “becomes” indicates the anagram.
6 BA (R EX) A M(ida)S Baa = lamb’s remark!
10 FERRYMAN Cryptic definition that I got first time around.
11 STATE OF PLAY Shakepeare’s play, Hamlet, is set in Denmark.
23 GREECE “Grease” 1970s musical set in the 1950s. Had never heard of bouzouki, so looked it up. It’s in the Concise OED as a mandolin played in Greece, so got the answer then.
24 Marlene DIET RICH
25 B (EAT) IT I think. Seems to fit wordplay, but definition = get, apparently, I’m not too sure about.
DOWN
1 B OUNCE Stock market term dead cat bounce.
2 WA(l)TER Mitty LEVEL
3 P (EER GYN) T (energy)* in pt = part. release indicates the anagram – I was looking for a long time for e = energy leaving something. This was only to check though because the answer I was familiar with.
5 ALPHABET “Stored in it all the letters one writes?” A magnificent cryptic defintion, with misleading context of a drawer or bureau.
16 NOR THE RN Line in the US, South of which lay the slave states and North the others.
19 SCREE N = Newton (unit of force – physics). Was looking for an anagram of Newton until I’d a confirmed crossing letter not among those six.
20 ABE D Remember Abe Lincoln
21 TUBE (r)
25A – you do find people in American cop shows saying ‘now get!!!’ meaning ‘beat it’. I took that to be it.