Contents of a flagon

ALE

Think of a frothy, fermented drink often served in medieval taverns, especially one brewed from malt and hops.

A flagon is a large container often used for serving beer or ale, so "contents of a flagon" directly points to a type of drink stored inside. The answer "ALE" fits because it’s a common alcoholic beverage historically carried in flagons, especially in British pub culture. No wordplay here—just a straightforward definition where the container hints at its usual contents.