Green’s Dictionary of Slang

1. (drugs) a bundle of the bottles in which crack cocaine is distributed, tied with a rubber band to facilitate carriage.

1992		R. Price Clockers 4: Selling bottles one for ten [...] On each clip he had been pulling in a hundred.
2001		ONDCP Street Terms 6: Clips — Rows of vials heat-sealed together.

2. (US) a pager [it is clipped to one’s belt].

2001

in ADS-L 🌐 Several students have informed me that ‘clip’ is now a term for pager, saying their acquaintances have used structures such as: ‘Call me on my cell or hit me on my clip.’.