Fastens up one's hair (5)
I believe the answer is:
locks
This clue could be a double definition.
'fastens' is the first definition.
(locking is a kind of fastening)
'up one's hair' is the second definition.
'locks' can be an answer for 'hair' (locks can mean hair). I'm not certain of the 'up one's' bit.
Can you help me to learn more?
(Other definitions for locks that I've seen before include "Securely fixes" , "Secures; person's hair" , "Fastens - hair" , "Clusters of hair" , "Door fasteners" .)