Initially jocularity offended killjoy even though they shouldn't have taken it seriously (4)
I believe the answer is:
joke
'they shouldn't have taken it seriously' is the definition.
The definition suggests an adverb but the answer is not.
'initially jocularity offended killjoy even' is the wordplay.
'initially' indicates taking the first letters.
The first letters of 'jocularity offended killjoy even' is 'JOKE'.
'though' acts as a link.
Can you help me to learn more?
(Other definitions for joke that I've seen before include "someone inadequate" , "something in cracker" , "Humorous remark" , "Gag" , "Crack in a cracker" .)