Embittered expert judged to have stolen book (9)

I believe the answer is:

acerbated

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'embittered' is the definition.
('acerbate' can be a synonym of 'embitter')

'expert judged to have stolen book' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'judged' becomes 'rated' (rating is a kind of judging).
'to have' is an insertion indicator.
'stolen book' becomes 'b' (abbreviation for book. I am not sure about the 'stolen' bit.).
'rated' placed around 'b' is 'rbated'.
'ace'+'rbated'='ACERBATED'

Can you help me to learn more?

I've seen this clue in The Guardian.

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