Idiot singer knocking bishop out (3)
I believe the answer is:
ass
'idiot' is the definition.
(both can mean a stupid person)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for ass that I've seen before include "Wally" , "Horse hybrid" , "One easily had" , "twit!" , "mug" .)