Merriment, in one spelling

GAYETY

Think of a lively, old-fashioned word for joy that starts with "gay" but isn’t the usual one.

"Merriment, in one spelling" hints at a less common but valid way to write "gaiety," which means cheerful liveliness. The answer is "GAYETY," an older variant spelling that swaps the i for a y—a trick crosswords sometimes use to test spelling knowledge. The clue plays on the idea that joy can be expressed in multiple forms, including this slightly archaic but correct version.