Chaps covered with slippery tar on deck (8)
I believe the answer is:
ornament
'deck' is the definition.
(I know that deck is a more specific form of the action ornament)
'chaps covered with slippery tar on' is the wordplay.
'chaps' becomes 'men' (chap means a man).
'covered with' is an insertion indicator.
'slippery' is an anagram indicator (I've seen this in other clues).
'tar'+'on'='taron'
'taron' anagrammed gives 'ornat'.
'men' placed within 'ornat' is 'ORNAMENT'.
(Other definitions for ornament that I've seen before include "deck" , "Trim" , "Something decorative" , "grace" , "to dress up" .)