It gets hit on the head (4)
I believe the answer is:
nail
'it gets hit on the head' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nail that I've seen before include "Growth on digit" , "Metal fastener" , "Fixer (on finger?)" , "Hits this in the head to be bang-on" , "SECOND PART OF 17" .)