Feeling of great joy (8)
I believe the answer is:
euphoria
'feeling of great joy' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for euphoria that I've seen before include "Exaggerated feeling of wellbeing" , "Feeling of great elation and joy" , "Sense of wellbeing" , "A feeling of wild happiness and well-being" , "Intense happy feeling" .)