Getting on in prison having got caught out (4)
I believe the answer is:
aged
'getting on' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for aged that I've seen before include "Antiquated" , "Time-worn" , "Advanced in years" , "not like a callow youth" , "Getting on" .)