Oasis and Nirvana dropping Ecstasy (5)
I believe the answer is:
haven
'oasis' is the definition.
('haven' can be a synonym of 'oasis')
'nirvana dropping ecstasy' is the wordplay.
'nirvana' becomes 'heaven' ('heaven' can be a synonym of 'nirvana').
'dropping' is a deletion indicator.
'ecstasy' becomes 'e' (informal term for the drug).
'heaven' with 'e' taken away is 'HAVEN'.
'and' is the link.
(Other definitions for haven that I've seen before include "Small port, refuge" , "Place of shelter" , "Harbour, oasis" , "Anchorage - retreat" , "Harbour - shelter" .)