The puzzle can be found here.
Hello everyone — I hope you are enjoying this bank holiday weekend. Thanks to Peter who has provided us with an enjoyable puzzle. Thanks also to Pierre who has provided me with the parsing of 15a.
Apologies for the briefer blog than usual. The weather is a little bit over me at the moment.
Definitions are underlined in the clues below. In the explanations, quoted indicators are in italics and I’ve capitalised and emboldened letters which appear in the ANSWER.
Across
1a   One taking the law into his own hands leaving IT in disarray (9)
VIGILANTE
LEAVING IT is anagrammed (in disarray)
6a   Advance payments for vehicles (4)
SUBS
Two definitions
8a   Nice plants woven round centre of wreath (8)
PLEASANT
An anagram of (… woven) PLANTS goes round the middle letters of (centre of) wrEAth
9a   Clever folk put fermented liquid into explosive (6)
TALENT
Follow the instructions in the clue and put ALE (fermented liquid) into TNT (explosive)
10a   Pet to beat? (6)
STROKE
A double definition. I’m hoping we’re beating the pet in a race or something … 
11a   Setter consumed by strange desire for drugs? (8)
REMEDIES
ME (setter) inside (consumed by) an anagram of (strange) DESIRE
12a   Part of window housing edges of principal display (6)
SPLASH
SASH (part of window) containing (housing) the outer letters of (edges of) PrincipaL
15a   Brief sign next to note about excessive text for musicians (8)
LIBRETTO
We have BIL[l] (brief sign), RE (note) and OTT (excessive), plus a reversal indicator “about” (though about could alternatively be RE), but I can’t quite get to the answer from the wordplay. Please help!
All but the last letter of (brief) LIBRa (sign of the zodiac), E (musical note), and the reversal of (about) OTT (excessive).   Thanks Pierre!
16a   Animal swallowing large seal swimming to get plant-based food (8)
COLESLAW
COW (animal) containing (swallowing) the combination of L (large) and an anagram (… swimming) of SEAL
19a   Come out of space with short green bananas (6)
EMERGE
EM (printer’s space) next to (with) most of (short) GREEn anagrammed (bananas)
21a   Brown cross over source of Indian dish (8)
TANDOORI
TAN (brown), then ROOD (cross) reversed (over), then the first letter of (source of) Indian
22a   Stop claiming runs where batsman stands (6)
CREASE
CEASE (stop) containing (claiming) R (runs)
24a   Spiritual lessons taken by poor author (6)
BARRIE
RI (Religious Instruction, Spiritual lessons) inside (taken by) BARE (poor)
25a   Insect tucked into ordinary banana (8)
PLANTAIN
ANT (insect) inside (tucked into) PLAIN (ordinary)
26a   Time meant to restrict online phenomenon (4)
MEME
TiME MEant is containing (to restrict) the answer.  Originally coined by Richard Dawkins in The Selfish Gene, the meme is now best known as the term for the cat pictures etc. much shared on the internet.  On Tuesday 14th May, one of my favourite memes decided to take a break from being alive — Grumpy Cat:

27a   Celebrity entertaining old time revolutionary in Parisian landmark (5,4)
NOTRE DAME
NAME (celebrity) containing (entertaining) O, (old), T (time), and RED (revolutionary)
Down
1d   Servant‘s farewell to Turkish leader (5)
VALET
VALE (farewell) + the first letter of Turkish (Turkish leader)
2d   Relative given most of out-of-date American breakfast dish (7)
GRANOLA
GRAN (relative) plus most of OLd (out-of-date), then A (American)
3d   Permission to depart (5)
LEAVE
Two definitions
4d   Regular tuna cooked with rocket and leeks for starters (7)
NATURAL
TUNA anagrammed (cooked) plus (with) initial letters of (… for starters) Rocket And Leeks
5d   Set arranged by setter’s qualified to be respected (9)
ESTIMABLE
An anagram of (… arranged) SET goes by I’M (setter’s) and ABLE (qualified)
6d   Special stick for 12? (7)
SPLODGE
SP (special) + LODGE (stick). 12a is SPLASH
7d   Device for tracking criminal placed under faulty U-bends in German parliament building (9)
BUNDESTAG
TAG (device for tracking criminals) following (placed under, in a down answer) an anagram of (faulty) U–BENDS
13d   Spread timber supporting roof of mine over stone (9)
PROPAGATE
PROP (timber supporting roof of mine) goes before (over, in a down answer) AGATE (stone)
14d   Spooky time in room over water at the beginning of November (9)
HALLOWEEN
The concatenation of HALL (room), O (over), WEE (water) and the first letter of (beginning of) November

17d   English language holding daughter back (7)
ENDORSE
E (English) plus NORSE (language) containing (holding) D (daughter)
18d   Punish favourite dog (7)
WHIPPET
WHIP (punish) + PET (favourite).  With this and 10a, Peter should perhaps beware of PETA
20d   Select raft to carry mythological princess (7)
ELECTRA
Here, sELECT RAft is containing (to carry) the answer
22d   Fabric in garment covering end of zipper (5)
CRAPE
CAPE (garment) containing (covering) the last letter of (end of) zippeR
23d   Small dish containing large plug (5)
SPILE
S (small) + PIE (dish) containing (carrying) L (large)
Bonjour Kitty.
15ac is LIBR[A], the zodiac ‘sign’ with its last letter missing, E for the musical note, and OTT reversed. Get well soon.
Merci bien Pierre. Blog updated.
I’m not sure if I have solved a Peter puzzle before. I found this one quite light, but I did enjoy it. I can’t recall having seen 22d spelt that way before and 23d was a new word for me but both were readily derivable from the wordplay. 7d was my favourite – what a great image the surface conjures up.
I was very sad to read about the demise of Grumpy Cat a couple of weeks ago – RIP in Cat Heaven.
Many thanks to Peter and to Kitty.
Should have been faster on the draw today – if I don’t get in before RD, I’m invariably left with the option of simply saying ‘ditto to RD’s comment’!
Seem to recall that I have solved some of Peter’s puzzles in the past – I remember being amused by Eimi’s comment that Loglady is a ‘he’ and Peter is a ‘she’!
Thanks to Peter for this one and to Kitty for the blog and the feline pics, greatly missed elsewhere. Get well soon, Kitty.
The spelling CRAPE was new to us (we generally think of ‘crêpe’ but according to Chambers CRAPE refers specifically to the black variety used in Victorian times for mourning. Apart from the possible obscurity of SPILE (it wasn’t to us) and the GK needed for BUNDESTAG we would say this would be an excellent puzzle for newbies in crypticland. No real favourites, it was all good.
Thanks, Peter and Kitty.
Good crossword from a setter whose name is a perfect match for one in The Guardian.
In 7d, I don’t think the BUNDESTAG is the name of that Berlin building. It is just the parliament housed in the Reichstag Building. That said, fine by me.
Thanks Kitty (take care!) & Peter.