Lock or ringlet (5)
I believe the answer is:
tress
This clue is a double definition.
'lock' is the first definition.
(both can mean a piece of hair)
'ringlet' is the second definition.
(I've seen this in another clue)
(Other definitions for tress that I've seen before include "Long piece of hair" , "Curl - lock" , "is a bit of a shock" , "Braid of hair" , "Switch" .)