Blissful state (7)
I believe the answer is:
'blissful state' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nirvana that I've seen before include "Buddhist 23" , "Kurt Cobain's grunge band" , "Transcendent state of Buddhists" , "Ultimate state in Buddhism" , "State of pure happiness" .)