Another challenging but immaculately constructed puzzle from Filbert for our Sunday entertainment. It took me my usual two sittings to complete this one, but I do enjoy tussling with this setter’s offerings.
Abbreviations
cd cryptic definition
dd double definition
cad clue as definition
(xxxx)* anagram
anagrind = anagram indicator
[x] letter(s) removed
definitions are underlined
Across
1 Undivided cooking apple on right of oven
OPEN-PLAN
(APPLE ON N)* with ‘cooking’ as the anagrind.
6 Notable partygoer brought back aboard oil rig tipsy
IT GIRL
Hidden reversed in oiL RIG TIpsy.
9 Hide pepper
PELT
A dd.
10 Cake British composer eats when the news is on?
BATTENBERG
An insertion of AT TEN in B and BERG.
11 Slow movement moving to Toscanini when piano comes in
CONSTIPATION
An insertion of P in (TO TOSCANINI)* The insertion indicator is ‘when … comes in’ and the anagrind is ‘moving’.
13 Small plane‘s crew’s using AM that cuts out at certain frequency
CESSNA
The odd letters of CrEwS uSiNg AM.
15 Iron front and back of shirt holding baby, objecting to it?
FEMINIST
An insertion of MINI in FE and ST for the outside letters of ‘shirt’. The insertion indicator is ‘holding’. An extended definition, which perhaps leads more to FEMINISM than FEMINIST, but nonetheless a great clue.
17 Snickers that’s disgusting after sandwiches
LAUGHTER
An insertion of UGH in LATER. The insertion indicator is ‘sandwiches’.
19 Nun‘s remains in nameless grave
SISTER
An insertion of IS in STER[N]. The insertion indicator is ‘in’.
20 Cravenly lose first of series – boozing essential
BOTTLE-OPENER
A charade of BOTTLE and OPENER.
24 Awkward part alongside Charlie Brown
CUMBERSOME
A charade of C for the NATO/phonetic alphabet ‘Charlie’, UMBER and SOME.
25 Fat dog on lead in field
FLAB
A charade of F for the initial letter of ‘field’ and LAB.
26 Junky lacking caution emptied twenty bags
TRASHY
An insertion of RASH in TY for the outside letters of ‘twenty’. The insertion indicator is ‘bags’.
27 Let an Irish priest on X?
TENANTED
A charade of TEN, AN and TED. The reference is to Father Ted, the TV series set in Ireland.
Down
2 Large tentacled creature raised behind pub is extraordinary
PHENOMENAL
A charade of PH for ‘pub’ and L ANEMONE reversed.
3 Some other people, presumably suggesting southerly wind
NOTUS
A charade of NOT US, suggesting ‘some other people, presumably’. NOTUS was the Greek god of the south wind, associated with the desiccating hot wind following the rise of Sirius in midsummer.
4 Running club train – it makes running easier
LUBRICANT
(CLUB TRAIN)* with ‘running’ as the anagrind.
5 Exceedingly hot in apartment and going up
NOT HALF
An insertion of H in FLAT and ON reversed. The insertion indicator is ‘in’. Reminiscent of Fluff Freeman, for those of a certain age.
6 Tribe from apparently glacial part of UK?
ICENI
A charade of ICE and NI for Northern Ireland.
7 Leave hands to become cracked
GO BANANAS
A charade of GO and BANANAS, which come in ‘hands’.
8 Excellent red at dinner
RARE
A dd. The second definition is referring to a RARE steak being served still red in the middle.
12 Swear idiot always spilled tea
ASSEVERATE
A charade of ASS, EVER and (TEA)* The anagrind is ‘spilled’.
14 Women’s group in US recalled eloquence of Lincoln
SUGABABES
A charade of US reversed, GAB and ABE’S.
16 Silly men heartless viragos lead to ruin?
MISGOVERN
(MEN VIR[A]GOS)* with ‘silly’ as the anagrind.
18 Rugby hooligan heard in bar
RULE OUT
A charade of RU and aural wordplay {‘heard’) for LOUT.
21 Remain black and sticky
TARRY
A dd.
22 The end Cervantes might have written, delicate and charming
ELFIN
Cervantes, being a Spanish speaker, would have written ‘the end’ as EL FIN.
23 King and queen flying north sound pleased
PURR
A reversal (‘flying north’, since it’s a down clue) of R, R and UP.
Many thanks to Filbert for this Sunday’s puzzle.

Clearly a slow morning in crossword land if I’m the first to reply to the blog an hour and a half after it was posted. Chapeau Pierre.
Yes, another elegant and testing puzzle from Filbert with some real twists: an excellent hidden disguising IT GIRL, that misleading def for CONSTIPATION, the neat defs for BOTTLE OPENER and LAUGHTER; the splendid spot of ANEMONE hiding in PHENOMENAL, the delightful surface for SUGABABES and the clever yet simple translation that results in ELFIN.
Thanks both