Nail him! (4)
I believe the answer is:
brad
I believe this is a double definition.
'nail' is the first definition.
(a brad is a nail with rectangular cross-section)
'him' is the second definition.
(Other definitions for brad that I've seen before include "Fixer" , "Small tapered nail" , "One to get hammered" , "Small tapering nail" , "It has a point" .)