Across
9 plate P<L(atvia)>ATE
10 Roosevelt ROO + EVE in S(pecia)>L + T(-shirt))
11 chaffinch CHA before FF + IN/CH(urch)
12 comic M(ahler) in 10/CC (anag) [10cc rock band]
13 stencil CLIENTS (anag)
15 coppers P(ortsmouth)/P(layers) in SCORE (anag)
17 minim M(otorway) + MINI (rev)
18 new double def
20 ideal cryptic clue (iDeal as Apple transaction)
22 courier (f/C)OURIER [Joseph Fourier]
25 century TUNE (anag) in CRY
26 times double def [eg 2 by 2]
27 mainstays MAIN<STAY>S
30 discounts DISCO + NUTS (anag)
31 lie-in N<I>EIL (rev) [Neil Diamond]
Down
1 epic E (Euler’s number) = 2.7138 + C (century, 25 across) ÷ PI (3.1416)
2 fava bean FAV<AB>E + AN [AB (able seaman)]
3 serf (plane)S/(her)E/(o)R/(of)F
4 Franklin (Anne) FRANK + L(earn)/1/N(ote)
5 Gothic GO + H(usband) in T(tme)/I/C(see)
6 perception PER + (con)CEPTION
7 meemie ME + ME (REV) + IE
8 otic (ex)OTIC
13 sumac SUM + A/C (account)
14 commission COMMI(e)’S SON
16 sully S(c)ULLY [Dana Scully]
19 wackiest W(ife) + CAKE IT’S (anag)
21 emulated E<MU>LATED
23 unmask M in SUNAK (anag)
24 Romans R<O(xygen)/MAN>S [Royal Society; Isle of Man]
26 tidy/Tidy double def [Bill Tidy]
28 sale jeruSALEm (hidden) [Manchester rugby club]
29 sans double def [sanatoria]