Fixing spike (4)
I believe the answer is:
nail
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fixing spike</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for nail that I've seen before include "Amall metal spike" , "Detect or catch (a criminal) (colloq.)" , "Covering on tip of the finger" , "Fasten - detect and expose" , "Growth on digit" .)