Inferior cell for old offenders (7)

I believe the answer is:

dungeon

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'inferior cell' is the definition.
'dungeon' can be an answer for 'cell' (I've seen this before). I'm unsure of the 'inferior' bit.

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for dungeon that I've seen before include "Underground prison-cell" , "part of prison" , "Dark prison cell" , "Dark place of confinement" , "Unpleasant cell" .)

I've seen this clue in The Globe and Mail.

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