FT 12,503 by Monk

A typically enjoyable and thought-provoking number from Monk.  I didn’t spot a trademark Nina, but I suppose that the four (4,5,4) answers that transect the grid symmetrically are, in themselves, a thematic touch.

Across
1 OP,H in TRY
4 ICE H(usband),OUSE – “Murder”=ice is worth bearing in mind if you are currently navigating the steeper parts of the learning curve in cryptic puzzles.
10 PE(I)G,NOIR – I never realised that Peg (the name) is a contraction of Margaret. A variant of Meg, I would assume.
12/13/14 FINE-TOOTH COMB – neat cryptic surface. It gave me flashbacks to images of the “nit nurse” visiting my primary school in those halcyon days of the late 70’s/early 80’s!
20 NEGATIVE SIGN (Gentian give)*
23/24/25 WIDE ANGLE LENS – another grid-wide cryptic surface combo.
28 DORMOUSE – “well known tea party” is a bit of a giveaway. Anybody care to name one other than the Mad Hatter’s, Boston’s or (at a stretch) chimpanzees’?
29 C,ACHED – simple and effective.
30 NO(R)SE,MEN – “neighbours” referring to SWEDEN at 21d.

Down
1 TRIFFIDS (first* around initial letters) – The TV adaptation of “Day of the Triffids” being the only programme that scared me more than Tom Baker and the Daleks during that aforementioned nit-nurse era.
3/15/26 HOME SWEET HOME (See how the memo)* – an astutely spotted angram, given the relatively limited selection of repeated letters.
5 CHESTERFIELD – the last one to go in for me, as I was slow on the uptake re: the furniture reference.
6,16,27 HIGH, WATER, MARK
7 (e)UROP(e),OD – Uropod was a new word for me, but checking and wordplay left little doubt. The surface reading is a little surreal, but it’s probably harsh to judge in comparison with the many excellent ones elsewhere in this puzzle.
11 MONTPARNASSE (Parsons meant)* – subtle use of “tour” in the definition.
19 O(NE,SID)ED – I’m not even going to try describing a Klein Bottle. This image link paints a thousand words.
21 SW(ED)EN – “regularly held”=ED