A “closer” or “stinger” is the antonym to “bumper” and “opener” in the world of radio broadcasting. Jingles are called “closer”, if they end a moderation. “Stingers” are often used in never-ending loops like music beds for announcements. At the end of the announcement a stinger is played for to signalise the viewer acoustically the end of the part in a content.
An example: During a radio newscast a report of a correspondent is inserted. At the end of the report a closer or stinger is used for that. The viewer realises the change back to the studio.