A police informant; a "rat".
Hey, I thought I got away with that burglary but my crime-partner pulled a McGruff on me.
Fight for Freedom. The "FFF" was a "gang" of basically what would now be called emo white boys in the San Fernando Valley ("The Valley") in the 1980's. FFF stuck together for a while (security in numbers) during the time when "real" Mexican and Black gangs began to take power in Los Angeles. FFF faded away as everyone grew up. White-boy gangs never really caught on in Los Angeles.
The "FFF" were a white boy gang in the San Fernando Valley during the 1980's. FFF stood for Fight for Freedom.