It gets hit on the head (4)
I believe the answer is:
nail
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">it gets hit on the head</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(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" .)