Triumphantly happy (8)
'triumphantly happy' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for jubilant that I've seen before include "Overjoyed" , "Elated" , "Triumphantly joyful" , "Showing extreme joy" , "Ecstatic" .)
(Other definitions for exultant that I've seen before include "Jubilant, rejoicing greatly" , "Triumphantly elated" , "Triumphant" , "Rejoicing greatly, delighted" , "really happy" .)