Jolliest (8)
I believe the answer is:
merriest
'jolliest' is the definition.
('merry' can be a synonym of 'jolly')
This is the entire clue.
(Other definitions for merriest that I've seen before include "Most jolly and high spirited" , "higher than the rest" , "Gayest, most jolly" , "Jolliest" , "most tipsy" .)