The most common and most likely answer to this crossword clue is the 15 letter word NON-PARTICIPANT
N
O
N
-
P
A
R
T
I
C
I
P
A
N
T
Buddy explains!
The straight part
We know that "he plays no role" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case he plays no role = non-participant.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.