scuffs

Had this scuff on left boot pretty early on and it's getting worse, Any idea what's caused it because I haven't really noticed it when riding.

what do you lot use to clean off your boot scuffs? especially from the rear tail piece? Im forever catching it with my boot as i get on and off and with the venture shield on it im worried that too much elbow grease may create problems? Ive tried spray on wax polish (zimoniz), wd40 but they...