Desert nation's competition (3,4)
I believe the answer is:
rat race
'competition' is the definition.
(I've seen this before)
'desert nation's' is the wordplay.
'desert' becomes 'rat' (abandon treacherously).
'nation' becomes 'race' (I've seen this before).
'rat'+'race'='RAT-RACE'
(Other definitions for rat race that I've seen before include "day-to-day struggle" , "keen competition" , "The daily grind" , "Rare cat (anag.)" , "The struggle for survival" .)