Tougher than usual Cincinnus perhaps with some challenging clues (for me 1A, 1D, 17D and 25D) and a couple of beauties (28A, 15D).
Across
1. LOBELIAS – ELIA (essayist) in LOBS (throws). It took me a while to figure this one out. “Essayist” immediately made me think of Charles Lamb whose writings I had enjoyed as a schoolboy but it had somehow escaped me that he was also know as Elia. Probably a good thing to remember for future crossword puzzles.
5. AGATHA – hidden word
9. VILLAGER – VI (6) + L (50) + LAGER (beer)
10. MINTON – MINT (perfect condition) + ON (aboard)
12. NIECE – E (egghead) in NICE (scrupulous)
13. REPELLENT – LEPER (outcast) backwards + LENT (advanced)
14. TIN CAN – INC (incorporated) in TAN (belt)
16. SYMPTOM – anagram of TOMMYS around P (platoon leader)
19. OVARIES – O (nothing) + VARIES (changes)
21. BETRAY – BET (wager) + RAY (fish)
23. ALBATROSS – A + L (large) + BAT (mammal) + ROSS (Polar explorer)
25. YIELD – double definition
26. DEGREE – DE (of French) + GREE[d]
27. DISCOVER – ISC (International Sales Conference) in DOVER (port)
28. RING UP – cryptic definition
29. PROTESTS – PRO (for) + TESTS (cricket matches)
Down
1. LIVING – double definition
2. BALLERINA – ERIN [poetic country] in BALLA[d] (unfinished poem)
3. LEASE – hidden word
4. ANEURIN – double definition
6. GUILLEMOT – I in GULL (bird) + TOME (book) backwards
7. TITHE – THE (article) about IT
8. AT NO TIME – anagram of TIE MAN TO
11. OPUS – O (overhead) + SUP backwards (drink up)
15. COINTREAU – anagram of A NEUROTIC
17. TEA LEAVES – TEAL (duck) + E (last of game) + AVES (birds). Tea leaves is a rather rare reference for thieves.
18. COLANDER – anagram of LARD ONCE
20. SHOT – S (small) + HOT (very attractive)
21. BUSTIER – cryptic definition
22. ADORES – anagram of SO DEAR
24. BEGIN – double definition
25. YACHT – AC (current) in THY backwards (your capsized)