Ground that is always frozen (10)
I believe the answer is:
permafrost
(Other definitions for permafrost that I've seen before include "Hard layer" , "Ground frozen for a long time" , "feature of polar regions" , "Ground never thawing" .)
I believe the answer is:
permafrost
(Other definitions for permafrost that I've seen before include "Hard layer" , "Ground frozen for a long time" , "feature of polar regions" , "Ground never thawing" .)