Secures hair in a bun, perhaps (5,2)
I believe the answer is:
locks up
'secures' is the definition.
(locking up is a kind of securing)
'hair in a bun perhaps' is the wordplay.
I cannot really see how this works, but
'hair' could be 'locks' (locks can mean hair) and 'locks' is located in the answer.
The remaining letters 'up' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for locks up that I've seen is " Confines (prisoner)".)