Unfashionable coiffure and cap (5)
I believe the answer is:
outdo
'cap' is the definition.
(I've seen this before)
'unfashionable coiffure' is the wordplay.
'unfashionable' becomes 'out' (synonyms).
'coiffure' becomes 'do' (synonyms).
'out'+'do'='OUTDO'
'and' is the link.
(Other definitions for outdo that I've seen before include "Perform better than, be superior to" , "Perform better than another" , "Surpass - overshadow - excel" , "Beat" , "Get the better of" .)