Fertile spot in desert, nothing like island (5)
I believe the answer is:
oasis
'fertile spot in desert' is the definition.
(I've seen this before)
'nothing like island' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'like' becomes 'as'.
'island' becomes 'is'.
'o'+'as'+'is'='OASIS'
(Other definitions for oasis that I've seen before include "Place of rest in the midst of gloom" , "quiet spot" , "Fertile place in a desert, watering-hole" , "English rock group in the desert" , "British band" .)