Boast of clothes worn back to front? (4)
I believe the answer is:
brag
'boast' is the definition.
(I know that boast can be written as brag)
'clothes worn back to front?' is the wordplay.
'clothes' becomes 'garb' (garb is a kind of clothes).
'worn back to front?' is a reversal indicator.
'garb' back-to-front is 'BRAG'.
'of' acts as a link.
(Other definitions for brag that I've seen before include "Card game - boast" , "popular with 15 [EGOTIST] , no doubt" , "Boast, exaggerate" , "game of bluff" , "Boast about garb" .)