Can refer to someone being killed or can refer to someone having nasty hardcore sex thus making a hard thumping noise which can resemble someone clapping their hands.
When you defend/hate/infatuated with a person or so passionately you seem to be sucking one’s meat to the point their balls are clapping against your chin.
"Clappin" is the act of having sexual relations with another person. This Word was originally used by metalheads from Berkeley California. See O.G. Bootyclap