Deep hole (3)
I believe the answer is:
pit
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">deep hole</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 pit that I've seen before include "Coalmine" , "Tip into crater" , "Tip into miners' shaft" , "Where racing cars refuel" , "Cherry stone" .)