Fifteensquared

An easy puzzle from Cincinnus with a few typically brilliant clues (1A, 13A, 18A, 5D).

Across
1. BEANS ON TOAST - anagram of NOT A SNOBS TEA. And a wonderfully English &lit to boot.
10. REEL OFF - double definition
11. EMIRATE - EMI (record company) + RATE (esteem)
12. CATCH - double definition
13. FLAGSHIP - FLAGS (ensigns) + HIP (with it)
15. PLAYTHINGS - double/cryptic definition
16. FAIR - F (fluorine) + AIR (mixture of gases)
18. TOPS - anagram of POST
20. SALAD CREAM - A (a) + LAD (young man) in SCREAM (something very funny)
22. TRUMPETS - E[legan]T in TRUMPS (best suit)
24. TRAIN - double definition
26. ORIOLES - RI (Rhode Island) in anagram of LOOSE. The Baltimore Orioles are a major-league baseball team. I am no sports fan but I know of the Orioles thanks to a friend who lives near Baltimore.
27. SATSUMA - A (a) + MUST (necessity) + AS (when) all backwards
28. GREENFINCHES - GREEN (inexperienced) + F (fellow) + INCHES (measures)

Down
2. ELECTRA - ELECT (chosen) + RA (artist). I did not know that Electra was Agamemnon’s daughter!
3. NEOPHYTE - anagram of THEY OPEN
4. ORFE - hidden word. The orfe is a freshwater fish found across northern Europe and Asia. It occurs in larger rivers, ponds, and lakes, typically in schools. (As I determined from Wikipedia.)
5. THEOLOGIAN - anagram of HOTEL IN GOA
6. AGING - A (a) + GIN (trap) + G (good)
7. TRACHEA - RAC (motoring organisation) in THE + A (articles)
8. PRECIPITATION - double definition
9. TEMPERAMENTAL - TEMPERA (paint) + MENTAL (up the wall!)
14. BIPARTISAN - I (one) in BP (oil company) + ARTISAN (skilled worker)
17. ECSTATIC - E[ton] C[ollege] + STATIC (still)
19. POURING - POUR (for French) + IN (in) + [avi]G[non]
21. ERASURE - ER (queen) + A (a) + SURE (certain)
23. PULSE - double definition
25. ASTI - hidden word