Gear to boast about (4)
I believe the answer is:
garb
'gear' is the definition.
(thesaurus)
'boast about' is the wordplay.
'boast' becomes 'brag' (brag is a kind of boast).
'about' says the letters should be written backwards.
'brag' reversed gives 'GARB'.
'to' is the link.
(Other definitions for garb that I've seen before include "Style of clothing" , "gear discovered" , "Covering" , "Dress - clothing" , "Attire, clothing" .)