Great fun from Guy this morning.
A well composed and immensely enjoyable puzzle. Many thanks to the setter!

ACROSS
1. Quiet smoke in bed, for baby’s parents (4,4)
PIPE DOWN
PIPE (smoke) + DOWN (in bed, for baby’s parents)
5. American’s cheap old book collected by fool (3-3)
TWO-BIT
O (old) + B (book) collected by TWIT (fool)
10. Frosty potato farmer’s left (5)
ALOOF
ALOO (potato) + F[armer] (‘s left)
11. Identifying mark on American cavalier’s weapon with cursory inspection (2,1,6)
AT A GLANCE
TAG (identifying mark) on A (American) + LANCE (cavalier’s weapon)
12. Light flickering is often concerning (3,2,4)
SET ON FIRE
(IS OFTEN)* (*flickering) + RE (concerning)
13. Pound found in street used in shop? (5)
SPENT
PEN (pound) found in ST (street)
14. Disorderly guy pinches silver Tesla (6)
RAGTAG
RAG (guy) pinches AG (silver) + T (Tesla)
15. Taking part, help Arab learn story of Jesus (7)
PARABLE
[hel]P ARAB LE[arn] (taking part)
18. Shape with six faces you’d say, each white (3,4)
CUE BALL
“CUBE” (shape with six faces, “you’d say”) + ALL (each)
20. Dislike of old creatures is blocking mammoth’s return (6)
AGEISM
IS blocking MEGA< (mammoth, <return)
22. Silent, one tucks into delicacy (5)
TACIT
I (one) tucks into TACT (delicacy)
24. Force unhappy children, perhaps painting picture of steps (4,5)
FLOW CHART
F (force) + LOW (unhappy) + CH (children) + ART (perhaps painting)
25. Infidelity Romeo enters into like a master? (9)
TREACHERY
R (Romeo) enters into TEACHER-Y (like a master?)
26. Make pretty odd choice from Auden? (5)
ADORN
A[u]D[e] OR N (odd choice from Auden)
Or to more clearly elucidate: A, D, or N are the odd letters in ‘Auden’
27. Warning light on cold slope down both sides (6)
CAMBER
AMBER (warning light) on C (cold)
28. Agent hears strange word again (8)
REPHRASE
REP (agent) + HEARS* (*strange)
DOWN
1. Force collects a commendation (6)
PRAISE
2. Lying judge given lead by Republican in office (9)
PROSTRATE
RATE (judge) given lead by (R (Republican) in POST (office))
3. The work of a certain journalist? (8,7)
DEFINITE ARTICLE
Cryptic definition – a play on words
4. Abrasive wife replaces husband in trial (7)
WEARING
[h]EARING (trial, W (wife) replaces H (husband))
6. Fall in NY with tall trees changing, Charlie spots (4,6,5)
WALL STREET CRASH
W (with) + (TALL TREES)* (*changing) + C (Charlie) + RASH (spots)
7. Head formerly supporting second grade (5)
BONCE
ONCE (formerly) supporting B (second grade)
8. Youthful period passed becoming bound by obligations (8)
TWENTIES
WENT (passed) being bound by TIES (obligations)
9. Bananas quietly blocked by EU? Not true (4,2)
MADE UP
MAD (bananas) + P (quietly) blocked by EU
16. Chief Italian sculptor missing the first dance (5,4)
BOSSA NOVA
BOSS (chief) + [C]ANOVA (Italian sculptor, missing the first)
17. Couple mid-barbecuing still happy (8)
ECSTATIC
[barb]EC[uing] (couple, mid) + STATIC (still)
19. Sent on flight full of teddy bears (6)
LOFTED
[ful]L OF TED[dy] (bears)
20. Turning one and twenty ultimately unexciting (7)
ANODYNE
(ONE AND [twent]Y (ultimately))* (*turning)
21. Expert catches 100 simultaneously (2,4)
AT ONCE
ACE (expert) catches TON (100)
23. The best bit of Carmen playing endlessly (5)
CREAM
CARME[n]* (*playing, endlessly)
DEFINITE ARTICLE
Shouldn’t we take
‘The’ as the definition
& the rest as the wordplay
(Certain DEFINITE, work of a journalist ARTICLE)?
Thanks Guy & Oriel
I parsed 3 down as KVa @1, and entering the answer allowed me to complete the North West quadrant quickly having been stuck there for a while. I thought this a very good puzzle, although a bit of a shame about the repetition of ONCE in 7 and 17 down. Many thanks tp Guy and Oriel.
Sorry that should be 7 and 21 down.
Never heard of “rag” for guy. Didn’t much like – or understand – the DOWN in 1ac. I know parents put their baby down to sleep but I don’t really think it works. Also not sure about cube giving cueb – the latter isn’t a word.
Despite these quibbles I did enjoy the puzzle with the top half going in quickly and the bottom half more slowly.
Quite a few where I got the answer straightaway and then parsed (or not).
Thanks Guy and Oriel
I liked ANODYNE, DEFINITE ARTICLE and CREAM. Fiona@4 rag and guy can both mean to tease or make fun of.
Thanks Guy and Oriel
14ac further to Petert@5: The relevant definitions in Collins 2023 are
guy 5 to make fun of; ridicule (p. 875)
rag² 1 to draw attention facetiously and persistently to the shortcomings or alleged shortcomings of (a person) (p 1646).
Neither of these has any regional indication, nor any marking as informal or slang.
By the way, I had 3dn the same way as KVa@1 and others.
Guy has become one of my favourite setters and this was another excellent outing. Struggled, but in a nice way, with only the “down” part of 1a giving me trouble along the same lines as Fiona @4.
I marked 3D as “double/cryptic definition,” as KVa@1. Many of the definition elements were themselves cryptic, which I sometimes had a hard time deciphering. Not an easy solve.
Good guy, or bad guy?
ECSTATIC, 17(d), seems too understated by the definition “happy”. I’m not one for superfluous wording, ( see below), but using “extremely happy” would create a potential misdirection ( outer letters ), whilst improving the accuracy of the synonym.
CAMBER, 27(ac), is equally a single slope, or a convex curve ( both sides of a road, to improve water drainage).
The single slope is possibly the more familiar, so “down both sides”, could be deleted, for an accurate but more concise clue.
PIPE DOWN, 1(ac): Nope, I don’t get it. What’s the “in” doing? Precursor to the definition? Well, “bed for baby’s parents” is meaningless. I must be missing something. I hope so, or this clue’s a stinker.
Notwithstanding, this is most definitely a Good Guy. Tricky but fair, great surfaces throughout, many smart devices.
Big thanks, Guy and Oriel.
“Is he DOWN?” the mother was asked on her return, after an absence to tend the fractious baby.
Thank you to Guy and Oriel.
Thanks for the blog , very good set of neat clues .
A baby in bed is definitely DOWN .
Thanks Guy. I found this slow going at first but somehow everything fell into place in a very satisfactory way. I never heard of ‘aloo’ as a potato so I couldn’t parse ALOOF but all else made sense. My favourites were SET ON FIRE, AGEISM, WEARING, LOFTED, and AT ONCE. Great stuff from an excellent setter. Thanks Oriel for the blog.
Tony@12 we have adopted a lot of Indian cuisine in the UK so many menus will include Bombay ALOO and saag ALOO , very firm favourites .
[Roz @13: We have many Indian restaurants in the US; I live within walking distance of 3 in my DC neighborhood. I’ve heard of vindaloo but I never connected that with ‘potato’ because I never saw potatoes in that preparation.]
[ Yes Tony , vindaloo as well but a bit hot . The two I mentioned just mainly potatoes and very popular here . ]
[Saag aloo – potatoes and spinach with a few spices – lovely]
[Aloo gobi: literally potatoes and cauliflower, one of my favorite veggie Indian dishes when done well. Available at most Indian places here. I’m sure they have it in DC too.]
Vindaloo (Goan) doesn’t have potato in it. It’s vinho and alho, Portuguese wine and garlic. So you can clue vindaloo using potato for the aloo without doing anything crass, except it’ll look like you have so you probably shouldn’t.
A solid and enjoyable puzzle. We weren’t too keen on DOWN; as parents (and grandparents) we can’t recall using the expression ourselves, but it was a long time ago now.
For 14ac we took ‘rag’ in the sense of ‘banter’, which Chambers gives as the first meaning in that context.
Favourites were ALOOF and LOFTED.
Thanks, Guy and Oriel.
Thanks all
Mostly enjoyable with Guy’s typical neat clues.
I ticked TWO BIT and ANODYNE for their surfaces, and TACIT for its misdirection. I did think a couple of clues were a bit too clever, but like others I enjoyed the variety and neat clues, and managed to get it all parsed.
Similar to Tony, I had never linked ALOO with potato, so good to learn. Good to learn about vindaloo too. For spinach dishes, I generally favor saag ghosht or palak paneer and cannot remember ever having saag aloo.
Thanks Guy and Oriel
Bossa nova is a musical style, not a dance.
Coby @ 21
from Chambers: “bossa nova /bosˈə nōˈvə/
noun
A style of dancing originating in Brazil, or the music for it”
The OED gives the two parts the other way round.
Wonderful
I too was puzzled by DOWN but having seen the explanation, I think it’s ok.
Fast becoming a favourite setter.
Firm but fair and definitely doable.
I enjoyed this a lot and while I understand common acceptance is that each can mean all and in fact is shown in chambers as acceptable synonym there is still something of about it I don’t buy. As in all people are equal but each person is equal. Or every person is equal. But all is clearly plural and each is not. anyways just my two bits! Thank you all
Too many pennies dropping, too late… mostly due to not seeing the definition till way down the line.. actually once filled in, it all made sense, so it was definitely a wavelength thing… even after I’d written PIPE DOWN in I was trying to see how that meant “parents”.. doh!
Thanks Guy n Oriel
Delightful puzzle from start to finish. I nominate 3d DEFINITE ARTICLE for Clue of the Month.
Thanks Guy and Oriel for the fun.