Across
Like ten to four on some watches (8)
Outlaw returned four-poster, say, under arrest (6)
Time put into needlework producing not a lot of note? (8)
Volume finished with old size of paper (6)
I haven't cracked this one yet — but Fifteensquared have:
QUART (a measure of “volume”) with O (old)
Contrive, in April, reorganised event featuring Irish quarters (15)
16a
Reversal of plain boundaries not proceeding in upright way (2,3,5)
See 15
Inside normal UFO, possibly, covering space and time (4-11)
In very small piece, it's certainly not square (4,2)
Male quadruped breaks barricades (8)
Sign name over two others, one of four famous ones (6)
I haven't cracked this one yet — but Fifteensquared have:
LEO (star “sign”) + N (name) over N + N (“two other” (names))
Four up, ominously, as the end approaches? (8)
Down
Economical inclusion of key in opening part of an Italian composition (7)
I haven't cracked this one yet — but Fifteensquared have:
Inclusion of A (“key”) in SPRING (“opening part of” The Four Seasons (“an Italian composition”))
Native from one quarter runs to here when thrown out (10)
eg sole four-letter word, in itself, is harmless (4)
Become aware of crew reportedly being summoned (4,3)
Not just 25% of invested capital held by one rich country (10)
I haven't cracked this one yet — but Fifteensquared have:
[ 25% of ] IN (vested) + QUITO (“capital”) held by I (one) + US (“rich country”)
Quartet unchanged by upsetting spell (4)
I haven't cracked this one yet — but Fifteensquared have:
If you spell ABBA backwards (or upwards in this case), it still spells ABBA.
One of four players, not a good one, in football club (4,3)
Making easier page without fourth line I penned in old language inside (10)
I haven't cracked this one yet — but Fifteensquared have:
L (line) + I penned in LATIN (“old language”) inside PAG (e) [ without fourth ] , so PA(L(L(I)ATIN)G
Four-wheeler put away, held by agent still? Not so (10)
I haven't cracked this one yet — but Fifteensquared have:
CAR (“four-wheeler”) + ATE (“put away”) held by (James) BOND (secret “agent”)
Reasons with number of Romans in specs, so to speak (7)
Husband wearing suit in domestic circles (7)
Part of format the writer used for book (7)
Needle that's four inches in length (4)
Observe 19's follower (4)
Type letters or click words in the clue