I found this puzzle quite tricky, and a complete contrast from yesterday’s yawn.  There were a good number of colloquialisms, but some clever twists and one or two clues  which defeated me, q.v below.

ACROSS

1.    - SERBIA  - (<res- bi -a{cres}
4.    - FLESH POT (I cannot explain this one.  Wanted to have ‘Pit’ as second word because of ’strip’,
                                 but could not fit in the ‘r’,  Help please?
9.    -  COD WAR  -(< ra- w- doc.  The conflict between fishermen of various countries over their rights)
10.  -  EARRINGS - (e-a-rring-s)- erring around Ann’s first letter with ’s’ from special
12.  -  MARZIPAN -  (m-ar-zip-an - feel that marzipan is only an addition to a cake, but am perhaps being  pedantic.
13.  -  FLEECE - (double definition)
15.  -  omitted
16.  -  APPEACH - ( someone will have to explain, please, why AP is a patronising label.  A nice archaic word. 20.  -  QUININE - ( quin-in-e {last letter of settee} )
21.  -   RILL - (< ll-ir from well-irrigated)
25.  -   HEANEY - (he-an -e -y)
26.  -  SEMILLON - (<no-l-lime-s - {l and s, 1st and last of Louis)
28.  -  TRIMARAN  - ( trim-aran ) - Aran sweater’s from Isle of Aran are very popular with boating people.
29.  -  COUPLE  -  ( coup-l-e - imagine the accent please in ‘coupe’..  A brace of people)
30.  -  PLEBEIAN  (- *be and alpine)
31.  -  CORTES  - ( escort with last two moved to front.  The legislative bodies of Spain and Portugal)
DOWN

1.   - SYCAMORE - (s-y-cam-ore - should the clue have been ‘wound up’ around etc. or have I got the word-                               play wrong?)
2.   -  RYDER CUP -(Ryder - c-up {for excited} - communicating indicates ’sound of’ rider. The golf  trophy        awarded every other year.)
3.   -  IN A FIX  -  ( *NAAFI without ‘a’,  plus IX for the team.)       
5.   -  LEAK- ( delicacy  prevents me from explaining!)
6.   -  SURPLICE  - (sur-*clip-e)
7.   -  PANZER -  (p- a-nz-e-r - PE around Australia and New Zealand, with last letter of war.  - the
                               tank developed in the 30’s by the Germans and used extensively in World War 2)
8.   -  TESTEE - (t-est-ee -) French for ‘is’, surrounded by tee- could be from golf or short for Tees river.)
11. -   omitted ( this time ‘cos I haven’t got the answer!)  
14. -  MEANDER -( me- and- ‘er )- a curving part of river also known as ‘oxbow’)
17. -  FUSELAGE - (fuse-lag-e ) - fusee needs the acute again - a kind of pyrotechnic lighting device.
18. -  LILLIPUT  -  (*tupil around ill)
19. -  FLANNELS - double definition
22. -  CHAT UP  -  (c-hat-up) -slang expression ‘ to pull’ - getting the lady between the sheets.                                      
23. -  DATIVE  - (dat-iv-e) - again, to date someone is to court in the old sense.
24 -  KIMONO - k-i-m-on-o (KO is to knock out in the boxing ring, hence ‘floor’)
27 -  HAKA - ( , New Zealand threatening chant before games - sounds like Hacker).

The usual, excellent, well-crafted, puzzle from Dac with good variety of treatments. Solving time, fast for me, 17 mins.

* = anagram < = reversed

ACROSS

1 SLIGHT Double definition

5 S (EAR) CH liked ear = something essential for listening in the context of the surface

8 SEND IN THE CLOWNS

10 REIN STATE

11 STILL Double definition Excellent surface with the divide at moving/picture

12 TOGGED (d e.g. got)<

13 MONS IE UR Mons (WW1 battle) Ur from Bible, well-known to solvers

16 HA (John) MILTON

18 DR OP IN Another brilliant clue

21 INLET Hidden

23 TAXIMETER (extra time)*

24 OPENING CEREMONY No 1 means first (in Greece m on pony)*

25 BEADLE How an American might say Beatle, I guess

26 TES TER(m) set< Very good, as containment is misleadingly suggested.

DOWN

2 LANCING

3 GAIT S KELL(y) Labour leader to 1963 Ruth Kelly, Cabinet member, I guess

4 TE TRAD

5 SKELETON (leeks not)*

6 ARLES hidden

7 COW (HID) E (s)

8 STRETCH L(I’M)O Lo = look one of those two-letter staples it’s worth getting to know.

9 SOLAR ENERGY (green)* in (royals)*

14 S TRUMPETS Good fun

15 MONTAG (U) E One the families from Romeo and Juliet

17 MO LIE RE French dramatist from the 1600s

19 PO (THO) LE (hot)*

20 EX TENT ‘of’ is a wordplay to definition link

22 THIRD if Alan Bennett = A Bennett Thora Hird = T Hird.

Mostly fairly straightforward, with a lot of anagrams, but the top left-hand corner had me stumped for a while. I particularly liked 2dn for its brilliant misdirection.