Slander retracted by bishop who's sorry - no words are necessary here (8)

I believe the answer is:

dumbshow

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'sorry no words are necessary here' is the definition.
I know nothing about this answer so I can't tell whether this works.

'slander retracted by bishop who's' is the wordplay.
I cannot quite understand how this works, but
'bishop' could be 'b' (abbreviation used in chess) and 'b' is found in the answer.
an anagram of 'who' is 'how' which is within the answer.
This may be the basis of clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Independent.

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