adverbial phrase. Essentially "trying not" or "trying to avoid" in standard English. The subtle difference between the slang standard English usages can be seen as follows: in standard English "not trying" simply means a failure to put forth any effort; whereas the slang meaning encompasses affirmative avoidance of responsibility, or steps taken to get out of an obligation.
Slang: Yo man now D not trying to pay me back.
Standard: D is trying to avoid paying me back.