FLIMSY provides this morning's fun…
A nice gentle and enjoyable start to the week, though I slightly dislike the "change" in 4d and 21d. Good surfaces all round though.
Thanks FLIMSY!

ACROSS
1. Disarm me at sea? They might (8)
MERMAIDS
5. In the morning, American editor’s occupied (6)
AMUSED
AM (morning) + US (American) + ED (editor)
9. Spot about to be covered by ointment (8)
LOCATION
CA (about) to be covered by LOTION (ointment)
10. Youtube finally releases episodes (6)
EVENTS
[youtub]E (finally) + VENTS (releases)
12. Caught fish east of island — it could be smoked (5)
CIGAR
C (caught) + (GAR (fish) east of I (island))
13. Academic performs so badly without money (9)
PROFESSOR
(PERFOR[m]S SO (without M (money)))* (*badly)
14. Left with one pound held in cash (6)
LIQUID
L (left) with I (one) + QUID (pound)
16. Food popular with setters? (3,4)
HOT DOGS
HOT (popular) with DOGS (setters)
19. Exemption from inhaling marijuana? Not initially (7)
FREEDOM
FROM inhaling [w]EED (marijuana, not initially)
21. Single out sailor with hook (6)
TARGET
TAR (sailor) with GET (hook)
23. Tangle almost tears net in harbour (9)
ENTERTAIN
(TEAR[s] (almost) NET IN)* (*tangle)
25. Cheer story about Spain (5)
ELATE
(TALE)< (story, <about) + E (Spain)
26. Large piece of wood maiden found in river (6)
TIMBER
M (maiden) found in TIBER (river)
27. I had gone round harsh area (8)
DISTRICT
(ID (I had))< (<gone round) + STRICT (harsh)
28. Diet regularly reduced father’s hunger (6)
DESIRE
D[i]E[t] (regularly reduced) + SIRE (father)
29. Threaten article probing changing gender (8)
ENDANGER
AN (article) probing (GENDER)* (*changing)
DOWN
1. Shy people concealing a lecturer’s spitefulness (6)
MALICE
MICE (shy people) concealing (A + L (lecturer))
2. Identify corgi seen barking (9)
RECOGNISE
3. Performer’s tarot cards partly turned over (5)
ACTOR
([ta]ROT CA[rds] (partly))< (<turned over)
4. Abandoned diamonds queen selected after a change of heart (7)
DROPPED
D (diamonds) + R (queen) + OPPED (selected (opted), after a change of heart (the T changing to a P))
6. Most I’ve wasted on a River Cruise? (5,4)
MOVIE STAR
(MOST IVE)* (*wasted) on A + R (river)
7. Police leader’s got no time for grasses (5)
SINGS
S[t]INGS (Police leader's, no T (time))
8. Is tenor wearing robe suffering? (8)
DISTRESS
(IS + T (tenor)) wearing DRESS (robe)
11. Relative picked up hot food (4)
NOSH
(SON)< (relative, <picked up) + H (hot)
15. Boxers perhaps constrained by sport (9)
UNDERWEAR
UNDER (constrained by) + WEAR (sport)
17. Adjust apron and I get working (9)
OPERATING
(APRON and I GET)* (*adjust)
18. Frantically feed cat — if not one’s upset (8)
AFFECTED
(FEED CAT [i]F (not I (one)))* (*frantically)
20. How one addresses a lady from the north or the south (4)
MAAM
Cryptic definition
"From the North or the South" suggesting the palindrome.
21. Retiree’s source of income beginning to change, creating anxiety (7)
TENSION
TENSION (retiree's source of income (pension), beginning to change (P changing to a T))
22. Teetotal — cutting alcohol makes you healthier (6)
BETTER
TT (teetotal) cutting BEER (alcohol)
24. Couples welcoming magician’s first spells (5)
TIMES
TIES (couples) welcoming M[agician] (first)
25. Former lover with mouth cut — one doesn’t speak on film (5)
EXTRA
EX (former lover) with TRA[p] (mouth, cut)
Thanks, Flimsy and Teacow!
Liked FREEDOM, SINGS and UNDERWEAR
DROPPED was the only one I couldn’t parse, and looking at the explanation here resulted in a groan. Letter-swapping clues are fine if we’re given a hint as to what the new letter might be. Same applies to TENSION. So I agree with you, Teacow.
Everything else was good fun, with no quibbles and no obscurities. Thanks, Flimsy.
Good start to week.
Although I understand the quibbles over changed letters one could argue that in 21d “beginning to “indicates that the new letter is T ?
Thanks to Flimsy and Teacow.
Hmmm … you’re being very generous, SM.
SM@3
An interesting interpretation, but I think it doesn’t quite work.
‘beginning to change’ indicates that the first letter (of pension) is to be changed.
Could a kind soul please explain how a police leader is a sting?
Kevin@6 Sting was the lead singer with the band The Police
Quite right , GDU and KVa. Happy to abandon my attempted explanation.
The only one I failed to parse was 7d
Now kicking myself very hard after seeing Billyk’s post.
Agree with Teacow’s ‘dislike’ of ‘the “change” in 4d and 21d’ – each telling us to alter a letter, but not telling us what to alter it to.
The crossers take care of that, for us, but we’d prefer to be told exactly what to do, in no uncertain terms, wouldn’t we?
Any significance that the former changes T to P and the latter changes P to T and the two are opposite each other in the grid?
DR OPTED PENSION producing DROPPED TENSION – some comment on the NHS crisis? Or are they just clunky clues?
I’d say the fact that both clues are clear and precise about which letter is to be changed makes them fair to the solver, and the definitions are straightforward enough that you can guess at the letter needed without without too much head-scratching. Plenty of checking letters for confirmation too. “Clunky” feels a tad harsh.
Anyway, I enjoyed it. MERMAIDS was my fave. Thanks, Flimsy and Teacow.
Thanks for the blog, a good set of clues , nice to see MERMAIDS , I see them early every morning.
I know it’s not really in the spirit of things, and I fully understand their justifications, and how one might figure them out, but I still get annoyed (perhaps not the right word, but it’s close) by clues such as 26A and ID, where M=maiden and L=lecturer . . . I’ve only been doing cryptics for about 3 years, and just do the FT and Guardian. Clues like that rarely if ever show up at the latter, but they seem fairly normal for the FT. Maybe one day I’ll get used to them.
Thanks Flimsy, that was fun with favourites being LIQUID, FREEDOM, DROPPED, MOVIE STAR, UNDERWEAR, and AFFECTED. I couldn’t parse TENSION. Thanks Teacow for the blog.
Eric@13 I do know what you mean but I think the setter has to use them sometimes to produce concise clues with clear wordplay. I have done the Guardian every day for 28 years and I think their setters are equally guilty.
Today we have M=master L=lake C=caught G=German and U=posh, this is only a sample of one puzzle and may not be typical but I will keep an eye on it.
As long as it is in Chambers and has some usage I always accept it.
Eric Eric @13
I am sure that you will eventually get used to the various conventions in crossword land. L for lecturer is a new one to me but M for maiden is used in cricket scoring when a maiden over ( no runs scored) has been bowled . The symbol is widely known but perhaps not by non- cricketers.
Roz and SM – thanks! But I used to play cricket, and sometimes even kept the score . . . and I know L for Lake, G for German etc. But L for Lecturer? Basically that’s just random, and seems more like the setter not being able to think of anything else. But I shall plod on . . . and it is just fun, after all.
Roz@15 Are you a crossword editor in another existence? Just from the way you said “I accept “. Maybe not I guess.
Eric @17 L = Lecturer is used in pay scales , various gradings .
Nick@18 I am just a fussy solver.
Roz, thanks, but I’m also sorry, because L as a lecturer in pay scales just made me laugh. And laughter is good. I shall go away now to B (which is used in this house to mean Bed).
GN EE
GM SM & EE
Re 4d and 21d, I’m with Widdersbel@11. I don’t think we need to have the required letter served to us on a plapper. 🙂
Thanks Flimsy and Teacow for the Monday merriment.