The most common and most likely answer to this crossword clue is the 10 letter word CO-STARRED
C
O
-
S
T
A
R
R
E
D
Buddy explains!
The straight part
We know that "shared billing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case shared billing = co-starred.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 CO-STARRED mean?
CO-STARRED verb- To perform with the billing of a costar.