Put casual clothes on carpet (5,4)
I believe the answer is:
dress down
This clue is a double definition.
'put casual clothes on' is the first definition.
(dress down can mean to dress casually)
'carpet' is the second definition.
(I've seen this before)
(Other definitions for dress down that I've seen before include "Severely reprimand; be informal" , "Reprimand - deliberately wear informal clothes" , "Adopt casual style (eg, on Fridays)" , "Scold - don't wear best clothes" , "Be unsuited" .)