The largest desert in the world (6)
I believe the answer is:
sahara
'the largest desert in the world' 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 "North African desert" , "Uncultivated region of north Africa" , "Great African desert" , "Great desert in N Africa" , "World's largest desert" .)