Horse step right? (5)
I believe the answer is:
pacer
'horse' is the definition.
(a horse which paces)
'step right?' is the wordplay.
'step' becomes 'pace' (pace is a kind of step).
'right?' becomes 'R' (common abbreviation).
'pace'+'r'='PACER'
(Other definitions for pacer that I've seen before include "Racing horse with an unusual gait" , "One setting race speed" , "Horse; one setting speed" , "Racehorse" , "Competitor" .)