Old man having part to play in prisoner's conditional release (6)
I believe the answer is:
Here is my best explanation:
'prisoner's conditional release' is the definition.
'old man having part to play' is the wordplay.
'old man' becomes 'pa' (both can mean father).
'having' says to put letters next to each other.
'part to play' becomes 'role' (I've seen this before).
'in' is the link.
(Other definitions for parole that I've seen before include "Word - condition of liberty", "Early release on promise of good behaviour", "Temporary release (of a prisoner)", "Temporary release on promise of good behaviour", "limited release", "Conditional release from imprisonment", "Early conditional release for prisoner in jail", "Release of prisoner promising good behaviour", "Provisional release (for prisoner)" and "Promise - conditional release".)