Boast about clothing (4)
I believe the answer is:
garb
'clothing' is the definition.
(garb is a kind of clothing)
'boast about' is the wordplay.
'boast' becomes 'brag' (synonyms).
'about' says the letters should be written backwards.
'brag' reversed gives 'GARB'.
(Other definitions for garb that I've seen before include "Raiment" , "gear discovered" , "Clothes to brag about" , "Attire, clothing" , "Outfit" .)