Hit with the head (4)
I believe the answer is:
butt
'hit with the head' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for butt that I've seen before include "Large cask" , "Fag-end" , "Use your head aggressively" , "What goat may do" , "Scapegoat - strike - bottom - barrel" .)