Arid expanse (6)
I believe the answer is:
desert
'arid expanse' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for desert that I've seen before include "Abandon - wilderness" , "Abandon - barren region" , "Run away from the forces; desolate" , "Abandon, waterless area" , "Abandon; arid region" .)