Hammer target (4)
I believe the answer is:
nail
'hammer target' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nail that I've seen before include "Brad, say" , "Horny covering of the digits" , "Finger feature (and tooth?)" , "Steel pin used by carpenters" , "Collar -- cop" .)