Clothing boast rebuffed (4)
I believe the answer is:
garb
'clothing' is the definition.
(I know that garb is a type of clothing)
'boast rebuffed' is the wordplay.
'boast' becomes 'brag' (synonyms).
'rebuffed' is a reversal indicator.
'brag' back-to-front is 'GARB'.
(Other definitions for garb that I've seen before include "Dress - habit" , "Clothe" , "gear discovered" , "Covering" , "Apparel, attire" .)