A while later, on leaving prison (5,1,4)

I believe the answer is:

after a time

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

'prison' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'a while later on' is the wordplay.
'while' becomes 'time' (I've seen this before).
'later' becomes 'after' (I've seen this before).
'on' says to put letters next to each other.
'a'+'time'='atime'
'atime' put after 'after' is 'AFTER A TIME'.

'leaving' acts as a link.

Can you help me to learn more?

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.