Green’s Dictionary of Slang

(US prison) to attack in a group, physically or verbally.

1998		Austin American-Statesman (TX) 4 Oct. 9/4: Texas Prison Gang Slang [...] Click: To attack or beat someone as a group.
2000		Other Side of the Wall: Prisoner’s Dict. July 🌐 Click: When two or more Inmates attack one inmate. ‘Those Inmates clicked on me.’ (TX).
2008		in J. Miller Getting Played 87: ‘[The boys] might just click on ’em and cuss ’em out, call ’em out they name’.