at a canter
Done or accomplished with ease or minimal effort. (A canter is a smooth, steady gait, as of a horse, which is between the pace of a trot and a gallop.) He was in such better condition than his competitors that he won the race at a canter.
in a canter
Done or accomplished with ease or minimal effort. (A canter is a smooth, steady gait, as of a horse, which is between the pace of a trot and a gallop.) He was in such better condition than his competitors that he won the race in a canter.