The den of a wild animal (4)
I believe the answer is:
lair
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">the den of a wild animal</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for lair that I've seen before include "Supposed large ape, the Bigfoot" , "Rail about wild animal's home" , "Home of a beast" , "enclosure" , "Wild animals' habitation" .)