How prisoner might remain uninformed? (4,2,3,4)

I believe the answer is:

kept in the dark

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'how prisoner' is the definition.
I can't tell whether this defines the answer.

'remain uninformed?' is the wordplay.
'remain' becomes 'kept' (I can't explain this - if you can you should give a lot more credence to this answer).
'uninformed?' becomes 'inthedark' (I've seen this in another clue).
'kept'+'inthedark'='KEPT IN THE DARK'

'might' acts as a link.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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