Dre is about to sing his verse; he is being called to the mic. Creeping is also driving and a phantom is a type of rolls-royce, so his flow or style of rap is smooth like a ride in an quality vehicle. "approach in a smooth, ghostlike manner"
Gotta break 'em off somethin' means to share the wealth or to give something meaningful to someone else. In the context of this particular part of the song, it means a very good song with a strong beat.
With all due respect, 'clockin a grip' doesn't have anything to do with guns. 'A grip' is slang for 'a lot.' So, what he's saying here is that he's making (clockin') a lot of money as a pimp. The Dolemite bit is pretty spot on though.
because of all the criminal activity Dr. Dre witnessed in Compton California, it was not unusual for the people of his neighborhood to find corpses of people who were murdered on Greenleaf Boulevard just north of Interstate 91
when you're driving putting one hand on the steering wheel and leaning either towards the passenger seat or out the window, all the while bumping to the beat. probably smoking a blunt