The most common and most likely answer to this crossword clue is the 4 plus 2 plus 7 letter word SONG OF SOLOMON
S
O
N
G
O
F
S
O
L
O
M
O
N
Buddy explains!
The straight part
We know that "celebration of love" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case celebration of love = song of solomon.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.