What the examiner did when one cheated (6)

I believe the answer is:

conned

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

'cheated' is the definition.
(conning is a kind of cheating)

'what the examiner did when one' is the wordplay.
I cannot quite see how this works, but
'when' could be 'on' (I've seen this in other clues) and 'on' is located in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for conned that I've seen before include "Deceived" , "Taken in, tricked" , "Studied; cheated" , "Studied carefully" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.