Vision of a distant oasis, maybe (6)
I believe the answer is:
mirage
'vision of a distant oasis maybe' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for mirage that I've seen before include "Optical illusion caused by atmospheric conditions" , "See it to believe it?" , "French flier" , "Illusory sighting" , "Illusions in the desert" .)