Boast about outfit (4)
I believe the answer is:
garb
'outfit' is the definition.
(thesaurus)
'boast about' is the wordplay.
'boast' becomes 'brag' (brag is a kind of boast).
'about' is a reversal indicator.
'brag' written backwards gives 'GARB'.
(Other definitions for garb that I've seen before include "Outfit" , "gear discovered" , "costume" , "Dress - habit" , "Attire, clothing" .)