Lairs (4)
I believe the answer is:
dens
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lairs</span>' is the definition.<br/ ><span class="explanation-format__explanation">('den' can be a synonym of 'lair')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dens that I've seen before include "Habitats of some wild animals" , "Man's" , "Habitations of wild animals" , "Lairs" , "Studies" .)