A formal affair is an event that is typically held in a formal setting and requires guests to dress in formal attire. The term 'formal affair' can refer to a variety of events, such as weddings, galas, and other special occasions. The crossword solution for the term 'formal affair' is BALL, which is a type of event that is often held in a formal setting. Balls are usually hosted by a host or hostess and involve dancing, music, and other activities.