Heel (3)
I believe the answer is:
cad
'heel' is the definition.
(both can mean a dishonourable person)
This is all the clue.
(Other definitions for cad that I've seen before include "Dishonourable man of decadent sort" , "Rogue" , "he's no gent" , "One behaves dishonourably" , "An Englishman who behaves dishonourably, a rotter" .)