Most lewd bishop with a group will pinch boss's rear (6)

I believe the answer is:

basest

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'most' is the definition.
Both the answer and definition are adjectives. Maybe you can see an association between them that I can't see?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for basest that I've seen before include "Most low or dishonourable" , "meanest?" .)

I've seen this clue in The Independent.

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