Cause that's a back track and I ain't tryna back that
Lupe doesn’t rap about selling drugs because he sees it as being something that is a bad influence on his fans and he says it would be labeled as a “bad track” in his opinon.
I think he says “…and I ain’t tryna back back” because, 1) he is continuing the idea that he doesn’t want to backtrack, and says he doesn’t want to back (as in walk backwards) back (as in backwards in time or as the better person he is now). And 2) I think he just repeated “back” twice because he had to fill the bar, or measure, for that line.
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