Depression; gap (4)
I believe the answer is:
hole
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">depression</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(depression can mean a hole or crater)</span><br/ ><br/ >'<span class="explanation-format__original">gap</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that hole is a type of gap)</span><br/ ><br/ ></span>
(Other definitions for hole that I've seen before include "Aperture; flaw in a plan" , "Opening on golf course" , "Well" , "mess" , "excavation" .)