Court security (4)
I believe the answer is:
bail
'court security' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bail that I've seen before include "Part of a wicket - legal payment" , "Sum of money guaranteeing the accused's return to court" , "Item resting on stumps" , "Temporary release of the accused - wicket crosspiece" , "Wooden bar" .)