Rotter or cad (4)
I believe the answer is:
heel
I believe this is a double definition.
'rotter' is the first definition.
(I've seen this in another clue)
'cad' is the second definition.
(I know that cad can be written as heel)
(Other definitions for heel that I've seen before include "Not the sole - scoundrel" , "See 1 down" , "Dog training command" , "horrible person" , "As a dog, obey" .)