Cad; body part (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)
'body part' is the second definition.
(heel is a kind of body part)
(Other definitions for heel that I've seen before include "instruction to setter, say" , "unpleasant type" , "Achilles's weak spot" , "Call to dog" , "horrible person" .)