Volcanic depression (6)
I believe the answer is:
crater
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">volcanic depression</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 crater that I've seen before include "Hole (on the moon?)" , "Feature visible on the moon" , "Large hole" , "Volcanic cavity" , "Bowl-shaped cavity, in a volcano say" .)