ACROSS
 1. MER CHANTS HIP = MERCHANT SHIP <cargo vessel>
 9. <wood> CEDAR = (.i)CED AR(b.)
10. <drink> CREAM SODA = REAMS inside CODA
11. WE ←LIVE← = WEEVIL <six-footer>
12. IRIS inside HOLD* = OLD IRISH <tongue>
14. <charge> FOSTERLING = FO_ + STERLING
15. F OR M = FORM <physique>
17. <train> LOCO <bats>
19. <flying vehicle> HOVERBOARD = OVERBOARD after H
22. TERRAIN outside P = TERRAPIN <shelled reptile>
23. MORAL outside T = MORTAL <deadly>
26. <soldier on> PERSEVERE = PER SEVERE
27. <how ashes may be> URNED = "EARNED"
28. NEW SPA PERM + A N = NEWSPAPERMAN <hack?>

DOWN
 1. <parrot> MACAW = M_ A_ CAW
 2. <remedy> REDRESS = RE DRESS
 3. HE ←SENIOR← = HEROINES <protagonists>
 4. <prison> NICK <alias>
 5. SLANDER outside ⭯THE⭯ = SHETLANDER <Scot>
 6. (I AM BIC) = IAMBIC <using poetic metre>
 7. DO + MO outside IN = DOMINO <mask>
 8. <got> FATHOMED = F (AT HOME) D
13. NEOLOGISMS* = GLOOMINESS <the blues>
14. ←(.k)SPITTLE F(l.)← = FELT TIPS <writers>
16. <utter> ABSOLUTE = A BS O_ + LUTE
18. CU RARE = CURARE <poison>
20. (NOT MANY)* = ANTONYM <opposition>
21. GAME _T _E = GAMETE <egg?>
24. L ADEN = LADEN <full of cargo>
25. GAVE* = VEGA <Lyra shiner>