What if learner turned into such a dunce? (4-3)

I believe the answer is:

half-wit

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'such a dunce?' is the definition.
I can't tell whether this definition defines the answer.

'what if learner turned' is the wordplay.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'turned' indicates an anagram.
'what'+'if'+'l'='whatifl'
'whatifl' anagrammed gives 'HALF-WIT'.

'into' acts as a link.

Can you help me to learn more?

(Other definitions for half-wit that I've seen before include "Fool" , "Hit flaw (anag.)" , "Nincompoop" , "Idiot" , "Stupid person" .)

I've seen this clue in The Sun.

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