Lock or plait (5)
I believe the answer is:
tress
I believe this clue is a double definition.
'lock' is the first definition.
(both can mean a piece of hair)
'plait' is the second definition.
(synonyms)
(Other definitions for tress that I've seen before include "Obsolete support" , "Bit of hair" , "Rests (anag.)" , "is a bit of a shock" , "Switch" .)