Hollow chamber in a hillside or underground (4)
I believe the answer is:
cave
(Other definitions for cave that I've seen before include "hole" , "Troglodyte's home" , "Primitive dwelling" , "Watch out" , "Natural underground chamber" .)
I believe the answer is:
cave
(Other definitions for cave that I've seen before include "hole" , "Troglodyte's home" , "Primitive dwelling" , "Watch out" , "Natural underground chamber" .)