A drug deal is going down between two rival gangs. The deal will be taking place either outside or in a club. When you reach the location, all of the enemies will appear on your radar as red blips. One of these enemies is carrying the stash. Keep killing the enemies until the stash is dropped; it will be appear on your radar as a dark green blip.
If the deal is taking place outside, you can use a Sniper Rifle from afar to thin the enemy ranks a bit, or you can drive in gun them down with an automatic weapon, an RPG Launcher, or a few Grenades.
If the deal is happening inside of a club, park outside, lock-on to the bouncer and shoot him dead. This will cause the enemies in the club to rush to the front door, allowing you to take them out with the Explosive Shotgun. Itís best to use Free Aim rather than auto-aim for this. Just keep the reticule trained on the front door and keep killing enemies as they appear until the drugs are dropped and the club is empty. If one or two of the enemies refuse to exit the club and the drugs havenít been dropped yet, head inside and take them out.
When you have the drugs, follow the highlighted route on your radar to the drop off to complete the mission. This video is from our unofficial game guide. You can view the full guide here