Dress up and show off (4)
I believe the answer is:
brag
'show off' is the definition.
(both can mean to boast about something)
'dress up' is the wordplay.
'dress' becomes 'garb' (synonyms).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'garb' backwards is 'BRAG'.
'and' acts as a link.
(Other definitions for brag that I've seen before include "Idle talk" , "boast; form of poker" , "Card game - boast" , "Show off, crow" , "popular with 15 [EGOTIST] , no doubt" .)