A more thorough explanation:

Definition: Ward-horn is a historical duty of keeping watch and ward with a horn to blow in case of a surprise attack. It was a part of the feudal duty that some tenants had to keep guard through continuous vigilance. The phrase denotes keeping guard by night (watch) and by day (ward).

Example: In medieval times, the lord of the manor would assign the duty of ward-horn to some of his tenants. They would keep watch and ward over the manor and blow the horn in case of any emergency.

Explanation: The example illustrates how ward-horn was a duty assigned to some tenants in medieval times. They had to keep watch and ward over the manor and blow the horn in case of any emergency. This duty was an important part of the feudal system and helped to ensure the safety of the lord's property and people.