Green’s Dictionary of Slang

clocking n.²

(US black) working as a drug seller.

1997

L. Pettiway Workin’ It 131: I know eventually I’m gonna get me a hit when I get outside anyway. See, as long as you got a tool for a person to use you’re gonna always get one. I smoke like thirty, forty caps a day. That’s average. Good days I’m busting loose. Oh, my goodness, fifty, sixty, seventy caps. Yeah, I’m busting. I’m constantly on a clock tip if it ain’t nothing but a dollar. Yeah, on a clocking. Meaning getting mines.

In compounds

clocking paper (n.) [paper n. (1)]

(drugs) profits from selling drugs.

2001

ONDCP Street Terms 6: Clocking paper — Profits from selling drugs.