The most common and most likely answer to this crossword clue is the 9 letter word REVELRIES
I've seen this crossword clue in The Sunday Telegraph
R
E
V
E
L
R
I
E
S
Buddy explains!

The straight part
We know that "celebration" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case celebration = revelries.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 REVELRIES mean?
REVELRIES noun- Joyful or riotous merry-making.