This is sung for joy (4)
I believe the answer is:
glee
'for joy' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for glee that I've seen before include "much fun" , "Unholy delight" , "(Malicious) satisfaction" , "Lively or triumphant joy" , "Great merriment" .)