hat

(n)

: A covering for the head, especially one with a shaped crown and brim.
As used in the common expression "Keep it under your hat"


club

(n)

: A group of people organised for a common purpose. A nightclub


hat-club

(n)

: An army of clubbers with a fanatical sense of fun, a panchant for quirky head-gear and a passion for filthy house music.
As used in the common expression "Don't talk about hat-club"