Thank you to Pangakupu. Definitions are underlined in the clues.
Across
8. Operation? It’s recalled in entertaining scam (8)
FUNCTION : Reversal of(…’s recalled) IT contained in(in) [ FUN CON](what you might call a scam/con that provides fun/is entertaining, if there is such a thing).
Defn: The activity/operation that is the purpose of a person or thing.
9. Way to contain heartless evil? Prepare to fire again (6)
RELOAD : ROAD(a thoroughfare/way) containing(to contain) “evil” minus its inner letters(heartless …).
Answer: To …, say, a firearm.
10. Encounter poor horse (4,4)
BUMP INTO : BUM(of poor quality/defective) + PINTO(a horse having irregular patches of two colours).
11. Composed piano line that’s sharp (6)
PLACID : P(abbrev. for “piano”, a musical term) + L(abbrev. for “line”) + ACID(sour/sharp-tasting).
12. Smart behaviour: vital part needs twist to work (5-10)
QUICK-WITTEDNESS : QUICK(the vital or central part, as in “… was cut to the quick by that remark”) + anagram of(… to work) NEEDS TWIST.
15. That chap’s seizing English ancient monument (5)
HENGE : HE(pronoun denoting “that chap”) containing(…’s seizing) ENG(abbrev. for “English”).
16. Demanding performer stands beside new bed (5)
DIVAN : DIVA(a demanding performer, one who is difficult to please) plus(stands beside) N(abbrev. for “new”).
… and storage:

20. Welcomes new ideas – is still producing coal, mostly by day (5,2,4,4)
KEEPS AN OPEN MIND : “keeps an open mine”(how you might describe one who continues to operate a mine producing coal) minus its last letter(mostly) plus(by) D(abbrev. for “day”).
21. US drink – intend coming back to consume seconds (6)
MIMOSA : Reversal of(… coming back) AIM(to pursue as an objective/intend) containing(to consume) MOS(plural of “mo”/a moment/a second).
Prosecco in lieu of champagne:

23. Underwear items about to be removed in clubs (8)
BRASSIES : “brassieres”(items of feminine underwear) minus(… to be removed) “re”(“with regard to”/about).
… what a No. 2 wood was.
25. Location of setter’s name? Tell joke about it – not half (3,3)
DOG TAG : [DO GAG](to tell/do a joke/gag) containing(about) “it” minus its 1st out of 2 letters(not half).
Defn: …, the setter being a breed of canine.
26. One sea swirling in major event covering large area (8)
EPIDEMIC : [ I(Roman numeral for “one”) + reversal of(… swirling) MED(short for the Mediterranean Sea) ] contained in(in) EPIC(grand/major).
Down
1. Cloudy burial mound with top hidden in cloud (7)
CUMULUS : C(abbrev. for “cloudy”, as in “pc”/partly cloudy) + “tumulus”(an ancient burial mound) minus its 1st letter(with top hidden, in a down clue).
… cotton woolly appearance.
2. What leads to misplaced refractor? It means extra work (5,5)
SCOPE CREEP : [SCOPE CREEP](cryptically, when an instrument with a lens, like a telescope, moves/creeps, it might lead to/result in a misplaced/dislodged refractor/lens).
Defn: …, when the requirements/scope of a project widens, usually after the project starts.
3. Pieces encapsulating current attitude (4)
MIEN : MEN(pieces in a chess set) containing(encapsulating) I(symbol for electric current in physics).
Defn: A person’s appearance or manner/….
4. Officer on street blocking large expenditure items (7)
ONCOSTS : [ NCO(abbrev. for “non-commissioned officer”) placed above(on, in a down clue) ST(abbrev. for “street”) ] contained in(blocking) OS(abbrev. for “outsize”/large).
Defn: …, in this case, overhead costs.
5. One from larger family, I’m last to dance such as waltz? (6,4)
TRIPLE TIME : TRIPLET(one of three children or animals born at the same birth, definitely making the family it belongs to, larger than usual) + I’M + last letter of(last to) “dance”.
Defn: In music, time or rhythm with tree beats to each bar, an example of which is/such as the waltz.
6. Some fanciful name for bone in wing (4)
ULNA : Hidden in(Some) “fanciful name”.
Defn: Bone in the wing of a bird, corresponding to the bone in a human’s forearm.
7. Communist leader, guzzling sherries, disposing of Nationalist criminal (7)
MAFIOSO : MAO(Zedong, Chinese Communist leader) containing(guzzling) “finos”(very dry sherries/fortified wines originally from Spain) minus(disposing of) “n”(abbrev. for “Nationalist”).
Defn: … who is a member of the Mafia, the criminal organisation.
13. Comedian’s good one repeated in Australian city (5,5)
WAGGA WAGGA : [ WAG(a comedian/joker) plus(…’s/has) G(abbrev. for “good”) + A(a single quantity/one) ] plus(repeated) WAGGA.
14. Trawler’s equipment cut, with ship surrounded by troops – collisions avoided (4,6)
NEAR MISSES : “net”(equipment of a trawler/a boat used for fishing with a trawl net) minus its last letter(cut) plus(with) [ SS(abbrev. for “steamship”, as used in the names of such ships) contained in(surrounded by) ARMIES(military troops) ].
17. Vegetarian’s opening no function that’s dished up meat (7)
VENISON : 1st letter of(…’s opening) “Vegetarian” + reversal of(… that’s dished up, in a down clue) [NO + SINE(a trigonometric function/ratio) ].
Defn: … from a deer.
18. Broad projection involving Times beginning to recruit influence in Parliament? (7)
LOBBYER : [ LOBE(a broad projection/a rounded part extending from a larger structure) containing(involving) BY(denoting multiplication/times, as in “2 by 2 = ..”) ] + 1st letter of(beginning to) “recruit”.
Answer: … or “lobbyist”, one hired to influence lawmakers/Parliament.
19. International difficulties elevated for now (7)
INTERIM : INT(abbrev. for “international”) + reversal of(… elevated, in a down clue) MIRE(trouble which is difficult to get out of/difficulties).
22. Unwilling to forgo large bond (4)
OATH : “loath”(unwilling/opposed) minus(forgo) “l”(abbrev. for “large”).
Defn: …/a solemn promise.
24. Song’s introduction missed in item from West Side Story (4)
ARIA : 1st letter(introduction) deleted from(missed in) “Maria”(an item/song from West Side Story, the musical).
Another challenging puzzle, with lots of witty clues and ULNA again the bone of choice. I liked BUMP INTO, QUICK WITTEDNESS, KEEP AN OPEN MIND, BRASSIES, EPIDEMIC, NEAR MISSES and INTERIM (topical). I can’t see any Nina and apart from there being four four-lettered clues, I can’t see a link to 44. I couldn’t parse CUMULUS.
Ta Pangakupu & scchua for the colour.
Well that was a struggle but very satisfying to finally reach the finishing line (which for me was INTERIM – couldn’t see the difficulties at first). Couldn’t help thinking there could be no such word as LOBBYER but it had to be right. Never heard of SCOPE CREEP and reverted to a word finder for that one. Always count reverting to that ploy as a fail on my part. Thanks all round.
Thanks Pangakupu and scchua
I usually enjoy this setter, but this puzzle not so much. A couple of solutions I had never heard of in 2d and 4d (I had heard “feature creep”), and several I couldn’t parse satisfactorily.
I hadn’t come across C for “cloudy”. Is it used in weather forecasts?
Favourite TRIPLE TIME.
Nice puzzle, but for me dog tags are not worn by dogs.
The problem of SCOPE CREEP was well known to me in my working life on IT projects. I’m sure it’s still a bugbear, particularly on government projects. LOBBYER was my LOI, but ONCOSTS was new to me. Hasn’t ULNA appeared in another puzzle recently? I was really pleased when I solved KEEP AN OPEN MIND as that helped enormously with the solve, as well as being a clever clue. No doubt someone with the requisite knowledge will reveal the nina before long.
Thanks to Pangakup and scchua.
I suspect the best known example of SCOPE CREEP is HS2.
For the Nina, I did wonder about TIKNSSA OCENIIM, but I have no idea how to space it – shoving that into Google translate Maori to English gets results for “Tiktok is so cute” and apparently there’s a TikTok trend “44 I’m so cute”. (After extensive use of search engines.)
Thank you to Pangakupu and scchua
Billy Mills @4: what would you call tags worn by dogs?
Nearly got there but defeated in the SE corner, having to reveal EPIDEMIC to break the deadlock.
Not wild about ‘C’ for cloudy and SCOPE CREEP was new. The Cousins use mission creep I believe, too define a project that fails to meet it’s key targets.
Toughie but goodie all in.
I’d heard of mission creep so SCOPE CREEP seemed plausible. AlanC has already picked my favourites. Shanne@6 That’s impressive detective work!
Nho ONCOSTS, but liked TRIPLE TIME. I’m not entirely convinced that FUNCTION=operation. One implies purpose and the other the means of achieving it.
If i had a pound for every time SCOPE CREEP was used in a meeting I would no longer have to work on these under resourced projects with unrealistic timelines.
Slightly intimidated seeing the grid shape and the setter but with the two long answers quickly in it was plainer sailing than usual for this setter.
Enjoyed KEEP AN OPEN MIND, BUMP INTO and HENGE amongst others.
Thanks Pangakupu and scchua
ONCOSTS, SCOPE CREEP, the great unknown. But apart from that and therefore a dnf, a nice puzzle from Pankakupu today. Particularly liked BUMP INTO and BRASSIES…
Re the nina: “The Forty-Fours are a group of islands in the Chatham Archipelago, about 50 kilometres (31 mi) east of the main Chatham Island. They are called Motchuhar in Moriori and Motuhara in Māori.”
https://en.wikipedia.org/wiki/Forty-Fours
Top row contains MOTU
Bottom row contains HARA
Loverly puzzle, Mr P, even if I was beaten by the mafioso. Ta for the graphic blog, scchua.
According to Google Translate, row 7 + column 13 – SRAS TEO OCENI IM – is Māori for “I’m sorry”. I wonder what for?