Become mature, with reprobate ways (5)
I believe the answer is:
ripen
'become mature' is the definition.
(I've seen this before)
'with reprobate ways' is the wordplay.
'with' means one lot of letters go next to another.
'reprobate' becomes 'rip' (informal term for a fraud).
'ways' becomes 'en' (I can't explain this - if you can you should believe this answer much more).
'rip'+'en' is 'RIPEN'.
Can you help me to learn more?
(Other definitions for ripen that I've seen before include "Become ready for eating" , "Grow older" , "Come to maturity like fruit" , "Get ready to open" , "Season" .)