Expert awfully nice about financial gain? The opposite (10)

I believe the answer is:

proficient

I'm a little stuck... Click here to teach me more about this clue!

'expert' is the definition.
(I know that expert can be written as proficient)

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for proficient that I've seen before include "Well-skilled" , "Showing skill" , "Competent, skilled" , "Able" , "having great facility" .)

I've seen this clue in The Guardian.

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