transmission or clutch?

Ok, so I have 2003 suzuki z400. Whenever I try to burn out, or sometimes when i get on it, it makes a grinding noise like something is slipping. let off and it stops. Also if im gonna get the front end up, and i let off the throttle completley and hit it, it does it too. but not if i keep pressure on it. Is it possible my clutch is shot? or is it my transmission? Need help please. Thanks Adam

It only happens when it is under extreme load. I am new to 4 strokes too, so any help you guys can offer would be greatly appreciated.

check you front sprocket i have seen them so worn that it will make a bad sound on a take off , as for the clutch ,its an 03 things do ware out