A racist slang term for a white person, because they're white like chickens. Derived from "cluck" the sound a chicken makes, and its similarity to "Klux" as in "Ku Klux Klan" who look even more like chickens then normal while people.
Vanilla Ice is such a cluc. I bet he learned how to dance from all his country club buddies.
C.L.U.C means Catching Lesbians Under Cover, which basically means proving that a girl is lesbian or did an act of unkindness.
"Dude, Katie. Did you hear what K-T Fresh , T-Simms and Jay-Fed, the members of the C.L.U.C, did to Jess last night? They found out she was a lesbian!" Todd said, shocked.