At prison was treated badly, but got through it (10)

'at prison was treated badly but got through it' is the definition.
I can't judge whether this defines the answer.

'prison was treated badly but got through it' is the wordplay.
I cannot really see how this works, but
'prison' could be 'pen' (both can mean an enclosure) and 'pen' is found within the answer.
an anagram of 'treated' is 'etrated' which is located in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?