Dress that's turned up to show off (4)
I believe the answer is:
garb
'dress' is the definition.
(I know that dress can be written as garb)
'turned up to show off' is the wordplay.
'turned up' is a reversal indicator.
'to show off' becomes 'brag' (both can mean to boast about something).
'brag' reversed gives 'GARB'.
'that's' acts as a link.
(Other definitions for garb that I've seen before include "costume" , "Clothes to brag about" , "Apparel, attire" , "something to wear" , "Fashion of dress" .)