'Do OK in exam?' 'Dunno' (4)

I believe the answer is:

pass

This clue is a double definition.

'do ok in exam?' is the first definition.

'dunno' is the second definition.
(e.g. response in a quiz)

(Other definitions for pass that I've seen before include "Blow over" , "Exceed; go by" , "Amorous advance" , "Eg, Khyber, Brenner" , "Go by; col" .)

I've seen this clue in The Everyman puzzle in The Observer.

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