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. I know for a fact that Phil's opponents have gotten better in the offseason, so I doubt he'll be able to win this one at a canter. The well-liked and highly-qualified candidate won the election 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. I know for a fact that Phil's opponents have gotten better in the offseason, so I doubt he'll be able to win this one in a canter. The well-liked and highly-qualified candidate won the election in a canter.

at a canter

without much effort; easily. British

At a canter is a horse-racing metaphor: a horse has to make so little effort that it can win at the easy pace of a canter rather than having to gallop.