Well by the context, 'i can whack at you' sounded more like something sexual...maybe I just misunderstood it.
So 'to whack at it' can mean 'to give it a try' and 'to try to hit' and 'to whack at you' just 'to give it a try'?
It has no sexual nuance that I know of, but it should be "take a whack at you." The verb whack by itself could have other nuances or meanings, but without more context I can't comment.
If a man and a woman are discussing whether they should try being a couple, one might jokingly say "I guess I'll take a whack at you." The original concept comes from a sport such as baseball, in which a player tries to hit a ball with a bat or something. So, to take a whack at something is to try to accomplish that thing.