Difference shown by prisoner getting fresh start (8)
I believe the answer is:
contrast
'difference' is the definition.
(thesaurus)
'prisoner getting fresh start' is the wordplay.
'prisoner' becomes 'con' (abbreviation for 'convict').
'getting' is a charade indicator (letters next to each other).
'fresh' is an anagram indicator (a fresh re-ordering of the letters).
'start' is an anagram of 'trast'.
'con'+'trast'='CONTRAST'
'shown by' is the link.
(Other definitions for contrast that I've seen before include "Dissimilarity of things compared" , "State of being strikingly different" , "Something completely different" , "Degree of difference in colour tones" , "Distinction" .)