Mingle enthusiastically with joy (4)
I believe the answer is:
glee
'joy' is the definition.
(I know that joy can be written as glee)
'mingle enthusiastically with' is the wordplay.
'with' says the answer is hidden in the clue.
'GLEE' is hidden within 'mingle enthusiastically'.
(Other definitions for glee that I've seen before include "Part song for men" , "Great pleasure" , "Type of club" , "much fun" , "Sort of club" .)