Long deep cut (4)
I believe the answer is:
gash
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">long deep cut</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for gash that I've seen before include "surplus to requirements" , "Long deep wound" , "Cut; waste (colloq.)" , "Jagged cut" , "Cut deeply" .)