In the Bible, Simon was no saint! (5)

I believe the answer is:

magus

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'saint' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see an association between them that I don't see?

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

Can you help me to learn more?

(Other definitions for magus that I've seen before include "Wizard" , "Guru" , "astrologer" , "Sorcerer" , "eg Melchior" .)

I've seen this clue in the Evening Standard.

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