Make fast arrest (4)
I believe the answer is:
nail
I believe this clue is a double definition.
'make fast' is the first definition.
(I've seen this in another clue)
'arrest' is the second definition.
(I know that arrest can be written as nail)
(Other definitions for nail that I've seen before include "Brad or tack" , "for the carpenter?" , "one wouldn't want in one's coffin?" , "Hit this on the head to be bang on" , "Horny covering of digit tip" .)