Bad woman in a good book (7)

I believe the answer is:

jezebel

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'bad woman' is the definition.
(thesaurus)

I don't understand the rest of the clue.

(Other definitions for jezebel that I've seen before include "Ahab's wicked wife" , "Ahab's wife (OT)" , "Shameless scheming woman in the Bible" , "Shameless or immoral woman" , "Biblical character" .)

I've seen this clue in the Evening Standard.

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