The most common and most likely answer to this crossword clue is the 7 plus 3 plus 6 letter word GILBERT AND GEORGE
I've seen this crossword clue in The Guardian
G
I
L
B
E
R
T
A
N
D
G
E
O
R
G
E
Buddy explains!
The straight part
We know that "Collaborative duo/Collaborative duo" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case collaborative duo/collaborative duo = gilbert and george.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.