Antarctic volcano (6)
I believe the answer is:
erebus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">antarctic volcano</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for erebus that I've seen before include "The abode of the dead" , "Volcanic mountain in Antarctica" , "God of darkness - cavern on the way to Hades - active volcano in Antarctica" , "In place of darkness" , "Greek god of darkness, son of Chaos" .)