The general theme of this section of the song is: "We have valuable assets which we like to display. We are also willing and capable of protecting them with physical force".
The original lyric is:
Come get, some, pistol grip, pump
If a nigga step on them white Air, Ones
"Come get, some" = I'm ready and not afraid of anyone.
"Pistol grip, pump" = the kind of gun he has.
"If a nigga steps on my white Air Ones" = If someone steps on my shoes. (relating to the previous sentence. ie. "I'll shoot someone if they step on my shoes").
"Come get, some, ____ grip, ____
"Gimmie six inches on them white, Air, Ones"
The first line is the same as above except some words have been blanked from the lyric track.
In the second line the meaning has been altered slightly.
"Gimmie six inches of space" is a phrase (though not a very common one) which means that someone is too close to you and you would like them to step away (the phrase can also be used to mean that someone is pestering/harassing you without being physically very close, but that's not how it's used here). By saying "On them white Air, Ones", he's implying that his shoes are special and are themselves worthy of personal space (perhaps even that he isn't afraid of the other person being so close to him, but he fears for his shoes). Either way, his shoes are the priority here.
Link to original song
Note: This answer is simply to help understanding. These lyrics should not be taken as an example of "correct" English. It is written in a particular style which is not commonly used (but adds greatly to the variety and creativity of the music). Some of the differences may be obvious, but others will not be. Be careful.