It's up with mirth when there's success around (7)
I believe the answer is:
triumph
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for triumph that I've seen before include "Victory - jubilation" , "celebrate victory" , "Exult in victory" , "Outstanding victory" , "Successful ending of a struggle or contest" .)