The most common and most likely answer to this crossword clue is the 5 plus 8 letter word RIGHT REVEREND
I've seen this crossword clue in The Daily Telegraph
R
I
G
H
T
R
E
V
E
R
E
N
D
More clues leading to the result RIGHT REVEREND
Buddy explains!
The straight part
We know that "Bishop" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bishop = right reverend.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.