Change criminal into saint? About right (10)
I believe the answer is:
transition
'change' is the definition.
(transition is a kind of change)
'criminal into saint? about right' is the wordplay.
'criminal' is an anagram indicator.
'about' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'into'+'saint'='intosaint'
'intosaint' with letters rearranged gives 'tansition'.
'tansition' going around 'r' is 'TRANSITION'.
(Other definitions for transition that I've seen before include "sort of element" , "Changeover" , "Process of change" , "Bridge" , "Switch" .)