The most common and most likely answer to this crossword clue is the 7 letter word BONKING
I've seen this crossword clue in The Guardian
B
O
N
K
I
N
G
Buddy explains!

The straight part
We know that "Enjoying oneself" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case enjoying oneself = bonking.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 BONKING mean?
BONKING verb- To strike or collide with something.
- To have sexual intercourse.
- To hit something with the front of the board, especially in midair.
- To experience sudden and severe fatigue in an endurance sports event due to glycogen depletion.
- A session of sexual intercourse.