Splendid bishop laughing about evil (9)
I believe the answer is:
brilliant
'splendid' is the definition.
(I know that splendid can be written as brilliant)
'bishop laughing about evil' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'laughing' becomes 'riant' (riant can mean cheerful or laughing).
'about' means one lot of letters goes inside another.
'evil' becomes 'ill' (I've seen this in another clue).
'riant' enclosing 'ill' is 'rilliant'.
'b'+'rilliant'='BRILLIANT'
(Other definitions for brilliant that I've seen before include "Magnificent" , "Very bright or vivid" , "Very bright; marvellous" , "Excellent; a diamond" , "Shining intensly" .)