Financial Times 12,902 by Mudd

Prize puzzle from the Weekend FT of 18 October
Mudd’s puzzle was the most difficult I have done in a while. I cannot figure out how 11A works.

Across
1. BACKHAND – BACK (second) + HAND (worker)
5. THRONG – R (right) in THONG (strip)
10. AORTA – hidden word
11. SINGAPORE – ???. I cannot see the wordplay here. Maybe I have the wrong answer but Singapore is the only word, never mind nation, that I can find that fits.
12. SCINTILLA – anagram of CALL IT SIN
13. HURST – S (small) in HURT (wound)
14. QUARRY – double/cryptic definition
15. TROLLOP – ROLL (turn) in TOP (spinner)
18. SEEPAGE – SEE (refer to) + PAGE (paper)
20. SNATCH – double definition
22. ALLAH – ALL (the world) + AH (purr). Is there a wee problem here? Seems to me that “purr” would fit but “purrs” does not.
24. ASCERTAIN – anagram of SECTARIAN
26. OSIER – [r]OSIER
27. RATTLE – double definition
28. AESTHETE – anagram of THE SEA + T[h]E

Down
1. BRAISE – B (book) + RAISE (up)
2. CERTITUDE – CE (church) + TIT (flier) in RUDE (offensive)
3. HEARTBREAK HOTEL – HEAR (try?) + anagram of TO BE THE LARK
4. NASALLY – NA (American) + SALLY (excursion)
6. HEATHROW AIRPORT – HEATH (PM prior) + ROW (war) + AIRPORT (forced)
7. ODOUR – O (nothing) + DOUR (grey)
8. GREAT APE – EAT (bite) in GRAPE (fruit)
9. IN FACT – anagram of CAN FIT
16. LUCRATIVE – U (posh) + CRAT[e] (old car almost) in LIVE (as it happens)
17. ISLANDER – I (I) + SLANDER (am less than complimentary)
19. ELAPSE – PALE (post) backwards + SE[nt]. Think pale as in impale!
20. SECRETE – SEC (dry) + RET (wet) + [spong]E
21. ENTREE – hidden word
23. LIMIT – MI (busy route) in LIT (illuminated)