Great question, its funny you asked, because I've thought of this a lot but have yet to try it out.
To me you need a couple of cones that can limit where the defense can go laterally, I would say these need to be fairly narrow, maybe the width of the free throw line.. Ideally you would want the defense to stay on the lateral plane, but thats not realistic so you also need to give him some room to move backwards so he can take an angle. So really the defensive would have a rectangular “zone” (maybe 12ft wide and 5 ft deep) that he's allowed to move in.
Now, how to play? I think there are a couple of different ways. In my mind this will be a fairly rough game, and I've thought about playing on the wrestling mats. One “rough” way would be to have the offensive player try to run through the zone. The defensive player's objective would be to try and touch the offensive player with his torso (or from the knees up to the chest)somehow. Guys will be getting run over hopefully, so you may not want to do this a lot. This would all be without a ball
Another way would be to have the offensive player run through the zone withought getting tagged. You'probably have to make the zone bigger, and it may not accomplish what you want as well, but you could use a ball easier with this one I think.
Just a couple of ideas.