Long-term convict
I believe the answer is:
lifer
'long-term convict' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lifer that I've seen before include "Rifle (anag.)" , "Prisoner serving the maximum term" , "Person serving long sentence" , "One with maximum sentence" , "One with very long sentence" .)