Performing properly wearing clothes (2,4)
I believe the answer is:
in gear
'performing properly' is the definition.
(in gear means performing well)
'wearing clothes' is the wordplay.
'wearing' becomes 'in' (you are 'in' the clothes you're wearing).
'clothes' becomes 'gear' (I've seen this before).
'in'+'gear'='IN GEAR'
(Other definitions for in gear that I've seen before include "Having shifted" , "Out of neutral?" , "Engaged" , "Ready to move (of car)" , "Dressed up" .)