Desert with a river in middle of Qatar (7)
I believe the answer is:
atacama
'desert' is the definition.
(Atacama Desert is an example)
'a river in middle of qatar' is the wordplay.
'river' becomes 'cam' (river in Cambridge, England).
'in' is an insertion indicator.
'middle of' says to take the centre.
The middle of 'qatar' is 'ata'.
'a'+'cam'='acam'
'acam' placed into 'ata' is 'ATACAMA'.
'with' is the link.
(Other definitions for atacama that I've seen before include "Chilean desert" , "lot of empty space" , "South American desert" .)