Drinking spot (5)
I believe the answer is:
'drinking spot' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oasis that I've seen before include "Britpop group" , "Manchester band featuring the Gallagher brothers" , "flower arranging stuff" , "A place of safety or sanctuary" , "Fertile tract in a desert" .)