Deep, dark hole (5)
I believe the answer is:
abyss
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">deep dark hole</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for abyss that I've seen before include "Primal chaos" , "Measureless chasm" , "Deep pit" , "Very deep gorge" , "Very large and deep chasm" .)