A very  pleasing puzzle, which I found quite easy.

Solving time: 22 mins

* =  anagram < = reverse

ACROSS

9 OVERT RUMP    Ruff (a term from the card game bridge, I think) = trump, then higher = overtrump.

10 OPER A     Repo<     Repossession

11 GARD A   Drag<     Irish policeman (from the Irish language = Guard)

13 PRIVATE (closed)  EQUITY (Actor’s Union)   A quick look does not turn the phrase up in dicts, but it was pretty straightforward.

15 RANCOUR  “Ranker”

17 OPEN AIR    Hidden reversal        Did not try to find anything out about the Siluarian epoch

19 APPLE TURNOVER

20 BEERS HEB A

21 NIFFY     Prob from (s)niffy, but I thought having a cold was sniffly, but no matter.

DOWN

1  Bjorn B(oy) OR G(irl)     Brilliant  “Old tennis player offered choice of children”

3 STRATI  (artist)*     Plural of stratus (a cloud)

5 UPSIDE-DOWN CAKES    i.e. buns< = snub!

6 BOUTIQUE   “Boo teak”

7  YE(s)MEN I    Next = naysayers

8 NAY  Dorothy SAYERS  (any)*

14 BROAD BAND

16 OBE IS ANT (soldier perhaps)

18 AERO FOIL!    That chocolate must be still around

20 PA ELLA

24 YET I

Just a short blog for this puzzle as many of the clues don’t really need much explaining. One thing you could never accuse Armonie of is unnecessary complexity in his clueing as the many of the clues have a Zen-like brevity to them and most of the answers rarely have more than two elements (eg, SUP,PORTER, TRAM, DE,ADMEN, PAST,E). For me, this made it a bit unexciting but if I was starting out on a solving career this is the sort of puzzle I would relish as a chance to fill a grid unaided.

If anyone would like an explanation for a clue not listed here, please leave a comment and I’ll do the honours.

This didn’t take me very long, and was short on elation in the solving.

Across
9 C EASE F IRE C for constant, ire is anger, ease is to moderate and f for fellow.
10 TANG O Number meaning a tune here, gnat is a fly set backwards against the last letter of Rio
11 OSCAR I didn’t like this clue much. You must have been in a cast to get one, but it is not awarded by a cast. Would it have been better as “Small statue one might get being cast”?
12 ROAST BEEF
13 AMPHOR A Camphor is sold as moth repellent. First taken off refers to the c, and then add ‘a’. Amphora are containers for liquids mainly used by the Greeks and Romans.
14 UNI FORM
17 TASTE
19 LID is slang for a hat. Not the most exciting clue.
20 P LEAD, P for piano, the musical term for quietly, lead being what the opening player does in Bridge.
21 CHAR LIE
22 QUARREL is a scrap, or fight, and also the short arrow, or bolt, used in a crossbow.
24 XY LOP HONE X and Y are mathematical symbols for unknown quantities.
26 HO TEL – tel is let (rented) turned.
29 GREEN ROOM is the hospitality room for performers or guests while they are not needed on stage or on camera in a TV studio.

Down
1 ECHO – some of thE CHOir.
2 MA D C AP
3 NE’ER DO WELL anagram of lender about owe L (for pound).
4 S I ERR A SA for South America, with I err inserted. A sierra is a rugged mountain range.
5 DE VAL U ED Val is the girl, and u sounds like you. The act is the ‘deed’ wrapped round.
7 ANTE LOPE Etna is the mount up, ie reversed. Lope is to run.
13 ATTIC, flight meaning stairs here.
15 IM PEACHING To peach is to betray. Impeachment is to be prosecuted.
16 ME D AL The Latin quingenti, or 500, is ‘D’. A gong is slang for a medal.
18 SCALLOP S is a tailless Pollack upside down in a ship. Interestingly enough the same ship could be full of Callop, which is the Golden Perch, right way up.
19 LIE DOG GO the dog or cur is trapped between a deception, lie, and a try, or go.
22 QUE B E C As the answer started with a ‘Q’ and with a reference to French Canada, the outcome didn’t seem in much doubt. BC is British Columbia. Que is French for ‘that’.
23 RATIO N a ration is a helping.
24 X RAY Not a lot of choice when it comes to answers starting with X.
25 PEAK –A homophone to pique, or stimulate, and to peek, for a quick look.