Deep gap (5)
I believe the answer is:
chasm
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">deep gap</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 chasm that I've seen before include "Deep opening in the ground" , "Deep fissure; gulf" , "Great divide" , "rent" , "One yawns" .)