A liberal smattering of general knowledge items (operas, chess players, Roman poets), of the type that one is either likely to know readily or have never heard of. I started off at a fair clip , but progress slowed to a crawl on the last two or three clues (particularly 17D).
PS: Belated apologies for absence from blogging last Friday. I carelessly forgot to remove myself from the roster before heading off on holiday.

Across
1 BECOME - double def’n
4 KARPOV - Reversal of [-D]vorak around p(enny) . Anatoly was world champion in the late 70s/early 80s and the Kremlin-favoured arch enemy of Gary Kasparov.
8 ENGORGE - (go green)*. A neat and cohesive clue.
9 MAN, DELA - “Island” instead of “Isle” to indicate Man caused me more trouble that it really should have.
12 G[-r]EEK
13 PILES - double def’n (these two being about as poles apart as I’ve ever encountered)
14 RE(P)LAYED - I briefly had REPEATED here before realising that I couldn’t justify it from the wordplay.
16 C(A TAP)ULT
18 LE(M)ON - M in Noel(Rev).
20 INCA - hidden alternate letters.
21 SLU(GP,ELLE)T - I have a grammatical quibble here; being under the impression that Elle in French equates to “she” rather than “her”.
23 FIDELIO - (Oiled, if)rev. I struggled to pinpoint a synonym for “squiffy” that was both short enough for the clue and polite enough for use in the FT!
25 FE[-a]STER
26 CYGNET - “signet”

Down
1 BAN,TU[-tu] - An appearance from Desmond Tutu, to complement the earlier one by Nelson Mandela. These days his claim to fame seems increasingly to be as a slang term for university degree classifications (2:2).
2 C,LO(A)CAL
3MOG(A,DISH)U[-l] - capital of Somalia. Synomymous with Black Hawk Down in the US.
6 POD,AGRA - I had to deduce this one from wordplay alone. It’s a specific form of gout (hence a “complaint”).
7 VEL(VET)EEN- Vet in (eleven)*. A bit tricksy in that here the number in the clue is refers to the anagram fodder itself, whereas in 18A it referred to another clue.
10 LUCRE,TIUS - (suit)rev
13 PLAIN,TIFF
15 POLYP,HO(N)Y - the surface reading here is a little thin, but probably not surprising given the disparity of the basic ingredients.
17 A(MADE)US - this alone took me several minutes to crack. “Produced down under” indicating Made in Aus(tralia). Probably better deserving of an exclamation mark than a question mark…
19 MUL,LION - “Chimney”=Lum, as in the Scottish phrase “Lang may your lum reek”.
21 SWIPE - double def’n.

The usual excellent crossword from Dac, hard enough (it took a while to get started), but not too hard. Everything, apart from one answer, went in slowly but regularly.