Former criminal, with leers (9)
I believe the answer is:
erstwhile
'former' is the definition.
(I know that former can be written as erstwhile)
'criminal with leers' is the wordplay.
'criminal' is an anagram indicator.
'with'+'leers'='withleers'
'withleers' is an anagram of 'ERSTWHILE'.
(Other definitions for erstwhile that I've seen before include "Quondam" , "Formerly" , "Former, previous" , "In the past" , "Former - list where (anag)" .)