Cad, rotter (4)
I believe the answer is:
heel
I believe this clue is a double definition.
'cad' is the first definition.
(I know that cad can be written as heel)
'rotter' is the second definition.
(I've seen this in another clue)
(Other definitions for heel that I've seen before include "Tilt" , "Crusty end of a loaf" , "Part of shoe; bad person" , "Lean over; part of foot" , "American rotter or shoe part" .)