Lines clothing to imitate part of jacket (5)
I believe the answer is:
lapel
'part of jacket' is the definition.
(I've seen this before)
'lines clothing to imitate' is the wordplay.
'lines' becomes 'll' (an abbreviation for line written twice).
'clothing' is an insertion indicator (some letters cover up or clothe others).
'to imitate' becomes 'ape' (synonyms).
'll' going around 'ape' is 'LAPEL'.
(Other definitions for lapel that I've seen before include "Continuation of a coat collar" , "Turnover at the front of a coat" , "Revere on a coat" , "Folded-back part of coat" , "Part of a folded back collar" .)