Battered hat, I am sure, is unprofessional (10)
I believe the answer is:
amateurish
'unprofessional' is the definition.
(synonyms)
'battered hat i am sure' is the wordplay.
'battered' indicates an anagram.
'hat'+'i'+'am'+'sure'='hatiamsure'
'hatiamsure' is an anagram of 'AMATEURISH'.
'is' acts as a link.
(Other definitions for amateurish that I've seen before include "using little craft, perhaps" , "Not very professional" , "Inept, unskilful" , "Lay" , "Unprofessional" .)