Desert people struggle to survive (3,4)
I believe the answer is:
rat race
'struggle to survive' is the definition.
(I've seen this before)
'desert people' is the wordplay.
'desert' becomes 'rat' (abandon treacherously).
'people' becomes 'race' (people can mean a national group or race).
'rat'+'race'='RAT-RACE'
(Other definitions for rat race that I've seen before include "unhealthy competition" , "tough competition" , "Continual routine of highly competitive activity" , "Competitive struggle for wealth or power" , "Daily struggle to get on" .)