African expanse (6)
I believe the answer is:
sahara
'african expanse' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sahara that I've seen before include "About 3,500,000 square miles of Africa" , "Great desert in N Africa" , "Great African desert" , "World's largest desert" , "North African desert" .)