A more thorough explanation:

Definition: Watch and ward was a duty in feudal times where certain tenants were required to keep guard through continuous vigilance. The phrase refers to keeping guard both at night (watch) and during the day (ward).

Example: In medieval England, watch and ward was a duty imposed on certain tenants who were responsible for keeping watch over their lord's property and protecting it from thieves and other dangers. They had to be vigilant both day and night, and were required to sound the alarm if they saw any suspicious activity.

Explanation: The example illustrates how watch and ward was a duty that required constant vigilance and protection of property. The tenants had to be alert and watchful at all times to ensure the safety of their lord's property. This duty was an important part of the feudal system and helped to maintain law and order in medieval England.