Some lifelong criminal (5)
I believe the answer is:
felon
'criminal' is the definition.
(I know that criminal can be written as felon)
'some lifelong' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'FELON' is hidden in the letters of 'lifelong'.
(Other definitions for felon that I've seen before include "convict" , "Serious criminal" , "Malefactor" , "Person guilty of grave crime" , "Wrong-doer" .)