Hair piece? (3)
'hair piece?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tress that I've seen before include "is a bit of a shock" , "Braid of hair" , "Obsolete support" , "Rests (anag.)" , "Curl - lock" .)
(Other definitions for wig that I've seen before include "rug" , "False head of hair" , "False hairpiece" , "Artificial hair" , "Artificial head covering, toupee" .)