Personality problem exemplified by Gregory? (11)

I believe the answer is:

egocentrism

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'gregory?' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'personality problem exemplified' is the wordplay.
'personality problem' becomes 'ego' (I've seen this in another clue).
'exemplified' becomes 'centrism' (I am not sure about this - if you are sure you should believe this answer much more).
'ego'+'centrism'='EGOCENTRISM'

'by' is the link.

Can you help me to learn more?

(Another definition for egocentrism that I've seen is " Self centred nature".)

I've seen this clue in The Times.

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