Polished boat parts up (5)
I believe the answer is:
sleek
'polished' is the definition.
(I've seen this in another clue)
'boat parts up' is the wordplay.
'boat parts' becomes 'keels' (I've seen this in another clue).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'keels' back-to-front is 'SLEEK'.
(Other definitions for sleek that I've seen before include "Elegant, streamlined" , "Aerodynamic - well-groomed" , "Looking prosperous" , "Smooth and shiny" , "with glossy coats" .)