Thank you to Lark. Definitions are underlined in the clues.
Across
1. Raised point, head surrounded by sea (8)
EMBOSSED : E(abbrev. for “east”, a compass point) + [ BOSS(head/leader of a group) contained in(surrounded by) MED(short or the Mediterranean Sea) ].
6. First people to claim welfare (6)
MAIDEN : MEN(people/about half of the human race) containing(to claim) AID(welfare/assistance to, say, the poor).
Answer: …, as in “maiden voyage”.
9. Element that could become another with time (6)
ERBIUM : Reverse clue: T(abbrev. for “time”) plus(with) ERBIUM makes(could become) “Terbium”(another chemical element).
10. Resident officer capsizing vessel with soldier (8)
OCCUPANT : Reversal of(capsizing) CO(abbrev. for “commanding officer”) + CUP(a vessel/a bowl-shaped container with a handle or handles) plus(with) ANT(insect living in in a society that has the caste of “soldier”) ].
11. Flesh-eating variant of coronavirus (11)
CARNIVOROUS : Anagram of(variant of) CORONAVIRUS.
13. Prosecutors‘ undeniable arguments (10)
PLAINTIFFS : PLAIN(undeniable/unmistakeable as in “it’s plain that it isn’t working”) + TIFFS(arguments/petty quarrels).
Defn: …/those who initiate legal proceedings against someone.
16. European discarding last flag? (4)
IRIS : “Irish”(European, specifically, relating to Ireland) minus its last letter(discarding last).
Answer: … flag or just flag.
17. Unearthed electrical components causing agitation (4)
FUSS : “fuses”(electrical components, viz. safety devices that break an electrical circuit if the current becomes excessive) minus(Un…ed) “e”(abbrev. for “earth”).
18. Leaders of national caucus encourage rejecting a false equivalence (10)
CONGRUENCE : Anagram of(… false) [ 1st letters, respectively, of(Leaders of) “national caucus” + “encourage” minus(rejecting) “a” ].
20. Writer encountering uproar about film healer (8,3)
MEDICINE MAN : ME(the writer using a self-referential pronoun) plus(encountering) DIN(an uproar/a noisy disturbance) containing(about) CINEMA(film/movies as an art or industry).
… treating a sick boy:
24. What Catholics did with some revolutionary figures in Italy (8)
LATINISE : Hidden in(some) reversal of(revolutionary) “figures in Italy“.
Defn: … re their liturgical rites.
25. Sound of Jersey wharf audibly muted (3-3)
LOW-KEY : LOW(the sound made by a Jersey cow/a moo) + homophone of(… audibly) “quay”(a wharf/a dock where watercraft moor).
26. Film of rapper in space (6)
ROMCOM : MC(derived from “master of ceremonies”, an alternative title for a “rapper”/one who performs “rapping”, a musical form of vocalisation) contained in(in) ROOM(space that can be occupied).
Defn: Short for “romantic comedy”, a genre of ….
As in When Harry Met Sally – “I’ll Have What She’s Having”:
27. Society men repeatedly having sex with unknown group of women (8)
SORORITY : S(abbrev. for “society”) + 2x(… repeatedly) OR(abbrev. for “other ranks”/non-commissioned men in the military) plus(having) IT(euphemism for “sexual intercourse”) plus(with) Y(symbol for an unknown quantity in mathematics).
Defn: …/female students in a US college or university.
Down
2. Humans preceded by our claim to be weird and wonderful (10)
MIRACULOUS : US(self-referential pronoun for you and I as members of the human race) placed after(preceded by) anagram of(… to be weird) OUR CLAIM.
3. Plant bons viveurs regularly sampled (5)
OSIER : 2nd, 4th, 6th, 8 and 10th letters of(… regularly sampled) “bons viveurs“.
From this:
to this: 
to this: 
4. Timid boys wandering around for days, exhibiting codependence (9)
SYMBIOTIC : Anagram of(… wandering) “Timid boys” with “C”(abbrev. for “circa”/around or approximately when refering to time periods) replacing(for) “d”(abbrev. for “days”).
Nemo’s back to safety and sustaining the anemone:
5. Leave to go to sleep (4,3)
DROP OFF : Double defn: 1st: To take someone or something to a place, and go off without them, as in “where shall I leave the shopping?”.
6. Chairman taking credit for big picture (5)
MACRO : MAO(Chairman … Zedong, former President of the Republic of China) containing(taking) CR(abbrev. for “credit”).
7. One meeting huge, overwhelming pressure without emotion (9)
IMPASSIVE : I(Roman numeral for “one”) plus(meeting) MASSIVE(huge/enormous) containing(overwhelming) P(symbol for “pressure” in physics).
8. What post isn’t being taken up mountain? (4)
ETNA : Reversal of(… being taken up, in a down clue) ANTE-(prefix indicating “before” and an antonym of/what … isn’t “post-“, indicating “after”).
Defn: …, specifically, the volcanic one in Sicily.
12. Upset with hellish performance? (10)
DISCONCERT : CONCERT(a musical performance) like/-ish DIS(hell/the underworld).
Defn: …/unsettle.
14. Sleepless in Seattle first, Raising Cain second (9)
INSOMNIAC : IN + 1st letter of(… first) “Seattle” + reversal of(Raising) [CAIN + MO(a moment/a second) ].
… 2 movie titles in the clue.
15. Something skated around and left hidden by agents – retro fire safety system (9)
SPRINKLER : [ RINK(an enclosed area of ice to be skated around on) plus(and) L(abbrev. for “left”) ] contained in(hidden by) reversal of(… – retro) REPS(short for “representatives”/agents, as in “sales reps”).
19. Setter coming up with cryptic clue to fill centre (7)
NUCLEUS : Reversal of(… coming up, in a down clue) SUN(the star that rises and sets on us daily) containing(with … to fill) anagram of(cryptic) CLUE.
21. Spiritual belief is embraced by American politician (5)
DEISM : IS contained in(embraced by) DEM(abbrev. for a member of the Democratic Party in the USA).
22. Gardening tool‘s propeller apparently doubles its velocity (5)
MOWER : “mover”(a propeller/that which causes movement) with its “v”(abbrev. for “velocity” in physics) changed to(apparently doubles …) “vv” or “w”.
23. Review of excellent board game for one who dislikes Othello (4)
IAGO : Reversal of(Review of) AI(or “A1″/first class/the best/excellent) + GO(a strategy board game, invented in China).
Defn: …, in Shakespeare’s play.
Thanks, LARK and scchua!
OCCUPANT
Is it not
CO (commanding) officer capsizing/reversing to become OC+CUP+ANT?
Thanks Lark and scchua!
Terrific puzzle. Needed parsing for a couple, thanks again.
Likes
FUSS
MEDICINE MAN
LOW-KEY
SORORITY
SYMBIOTIC
CONGRUENCE
You’re right, KVa. Thanks. Blog corrected.
Lots to love here. The nice spot of CINEMA hiding in 20a and, taking top place, the wonderful clue for INSOMNIAC. I also liked the use of ‘wandering around for days’ in 4d amongst other clues. Bravo!
Loved the puzzle. Managed all unassisted except for 9a. I hope I wasn’t the only one needing a periodic table.
Thanks Lark and scchua.
AJG @5. Me too. Didn’t know either of them.
https://en.wikipedia.org/wiki/Ytterby
How’s this for imagination? – A Swedish village – not even a town or a city – with a boring name that translates to “outer village” has four elements named after it.
yttrium (Y), terbium (Tb), ERBIUM (Er), and ytterbium (Yb)
They could have at least anagrammed the last one and named it after BETTY Rubble – BETTYRIUM
INSOMNIAC – Yes, I am, Thanks L&s
FrankieG@7
Quite an interesting article.
FrankieG
Btw: Read your post on ‘dock brief’. Thanks.
Shooting off to a food and drink festival so a very quick note to record my thanks to Lark and scchua. I found this tough, this morning. Beaten by a couple – entirely my bad – and by the element. Lots to like.
KVa@8 – “Quite?” – I’m assuming sense 3 – fairly, a bit, mildly. 🙂
Adverb – quite (not comparable)
1 To the greatest extent or degree; completely, entirely.
2 In a fully justified sense; truly, perfectly, actually.
3 To a moderate extent or degree; somewhat, rather. [from 19th c.]
KVa@9 – well that makes one of you. 🙂
Quite an analysis!
Thanks both. I immediately knew ERBIUM would defeat me, as the intention was clear but playing to a void in my knowledge, and so it proved. ETNA got me to thinking about ante-post odds in betting, which kind of becomes an oxymoron, the latter part of which adequately describes my typical performance at a race course
Failed by not knowing either of the elements at 9a; thanks for the fascinating article, FrankieG @7. That was on top of some other hard ones so I was fortunate not to have missed more. Thanks for explaining MOWER; I was on the right track but just couldn’t figure it out. I missed the theme in Lark’s last puzzle but FWIW couldn’t see one today.
I did note when solving that ‘capsizing’ at 10a was needed for the surface but strictly speaking a reversal indicator wasn’t otherwise essential as both CO and OC can mean an officer in a position of authority.
Thanks to scchua and to Lark
Fortunately, I knew the first element but did have to check on the second. Found bits of this one quite tough but overall an enjoyable solve. That reminder of Meg Ryan’s scene always makes me laugh, particularly the order subsequently sent in by her neighbouring diner!
ROMCOM & CARNIVOROUS sharing the honours for me.
Thanks to Lark and to scchua for the review.
IMO, 26a is MC [rapper=hammer>>MC HAMMER an erstwhile famous rapper (rhythmic speaking set to a beat)] contained in ROOM for ROMCOM
ROmcOM “26 Film of rapper in space (6)…27” – a shout-out to the blogger mc_rapper67
last seen blogging Arachne‘s Guardian Prize farewell tribute to Nutmeg.
‘Noun – shout out (plural shouts out) – (entertainment) – An unscripted mention of the name of a viewer or audience member when on stage, television, etc.
A section of a web page, profile or blog containing these greetings.’
‘Recent Examples on the Web – “Its effectiveness even got a shout-out on a recent episode of The Bear.'”- Camryn Rabideau, Peoplemag, 14 July 2023′
[Here’s my shoutout: The Christmas episode of The Bear – (Season 2, Episode 6 ‘Fishes’) – is absolutely brilliant – a dead cert to win Emmys in 2024.
Come back here next year and see if I’m wrong. (“As if…”)]