Rats in areas of wasteland (7)
I believe the answer is:
deserts
This clue is a double definition.
'rats' is the first definition.
'areas of wasteland' is the second definition.
'in' is the link.
(Other definitions for deserts that I've seen before include "Sahara and Gobi" , "Arid areas" , "Abandons; barren places" , "Appropriate rewards" , "barren areas" .)