Cavern, in poetry (4)
I believe the answer is:
grot
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">cavern in poetry</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 grot that I've seen before include "Refuse" , "Filth" , "tat" , "Rubbish (slang); picturesque cave (poet.)" .)