Arrest Brad (4)
I believe the answer is:
nail
I believe this is a double definition.
'arrest' is the first definition.
(I know that arrest can be written as nail)
'brad' is the second definition.
(brad is a nail with rectangular cross-section)
(Other definitions for nail that I've seen before include "stud" , "Metal fastener" , "Hammer's target" , "Hammered individual" , "one wouldn't want in one's coffin?" .)