The most common and most likely answer to this crossword clue is the 11 letter word CELEBRATING
I've seen this crossword clue in The Guardian
C
E
L
E
B
R
A
T
I
N
G
More clues leading to the result CELEBRATING
Buddy explains!

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 CELEBRATING mean?
CELEBRATING verb- To extol or honour in a solemn manner.
- To honour by rites, by ceremonies of joy and respect, or by refraining from ordinary business; to observe duly.
- To engage in joyful activity in appreciation of an event.
- To perform or participate in, as a sacrament or solemn rite; to perform with appropriate rites.
- Celebration