The most common and most likely answer to this crossword clue is the 8 letter word GRUNTLED
G
R
U
N
T
L
E
D
More clues leading to the result GRUNTLED
Buddy explains!

The straight part
We know that "jokingly happy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jokingly happy = gruntled.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does GRUNTLED mean?
GRUNTLED adjective- Grunted.
- Satisfied, pleased, contented.