Parts of ships, smooth and glossy when done up (5)
I believe the answer is:
keels
'parts of ships' is the definition.
(structures on the bases of ships)
'smooth and glossy when done up' is the wordplay.
'smooth and glossy' becomes 'sleek' (I've seen this before).
'when done up' says the letters should be written in reverse.
'sleek' written backwards gives 'KEELS'.
(Other definitions for keels that I've seen before include "bases of vessels" , "Parts of ships" .)