Lapel back incomplete (6)
I believe the answer is:
revers
'lapel' is the definition.
(revers is a kind of lapel)
'back incomplete' is the wordplay.
'back' becomes 'reverse' (I've seen this before).
'incomplete' means to remove the last letter.
'reverse' with its final letter taken off is 'REVERS'.
(Other definitions for revers that I've seen before include "Lining" , "Part of garment" , "One turns back" , "a turn-up for the cloth?" .)