Former criminal to go straight
I believe the answer is:
re-form
'go straight' is the definition.
(I've seen this before)
'former criminal' is the wordplay.
'criminal' indicates anagramming the letters.
'former' is an anagram of 'RE-FORM'.
'to' acts as a link.
(Other definitions for re-form that I've seen before include "Give up evil ways, go straight" , "Remedy abuse" , "Mend ways, abandon evil practices" , "Mend ways, go straight" , "Give up old ways and change for the better" .)