Learnt off earnestly? Of course! (3)

I believe the answer is:

yes

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

'of course' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for yes that I've seen before include "Validating vote" , "Affirmative response" , "Absolutely" , "3 across" , "Agreed" .)

I've seen this clue in the Irish Times.

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