Wear out high-stepping horse (7)
I believe the answer is:
hackney
This clue is a double definition.
'wear out' is the first definition.
(hackneyed means worn out or cliched)
'high-stepping horse' is the second definition.
(type of horse)
(Other definitions for hackney that I've seen before include "Carriage for hire" , "district of London" , "Wear out" , "Old cab - London borough" , "draught horse" .)