See chess piece, rook, taken by one -- first of castles (9)
I believe the answer is:
Here is my best explanation:
'see' is the definition.
'chess piece rook taken by one first of castles' is the subsidiary indication.
'chess piece' becomes 'bishop' (bishop is a kind of chess piece**).
'rook' becomes 'r' (abbreviation in chess).
'taken by' says to put letters next to each other.
'one' becomes 'i' (roman numeral).
'first of' suggests taking the first letters.
The initial letter of 'castles' is 'c'.
(Other definitions for bishopric that I've seen before include "position of a minister", "Episcopate", "Church office", "Diocese", "See - diocese" and "Phobic sir (anag)".)