Nothing unaltered in desert haven (5)
I believe the answer is:
oasis
'desert haven' is the definition.
(I've seen this before)
'nothing unaltered' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'unaltered' becomes 'asis' (ie something left 'as is').
'o'+'asis'='OASIS'
'in' acts as a link.
(Other definitions for oasis that I've seen before include "Florist's foam" , "Area of calm amid hectic surroundings" , "place of relief" , "Pop group" , "Safe haven" .)