Dress card game up (4)
I believe the answer is:
garb
'dress' is the definition.
('garb' can be a synonym of 'dress')
'card game up' is the wordplay.
'card game' becomes 'brag' (I've seen this before).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'brag' in reverse letter order is 'GARB'.
(Other definitions for garb that I've seen before include "Covering" , "Apparel, attire" , "Fashion of dress" , "gear discovered" , "costume" .)