clip overlapping

In Multitrack view, go to the Window menu, and make sure that there's a check in Properties. Now, the Properties tab will appear - by default I think it's in the same group of tabs that has the Effects Rack in it. Select it, and proceed as above.

But most significantly here is that it seems that you haven't really understood how Multitrack works, because if you had, you wouldn't be worried about this at all! If you have a load of tracks that you want the same effect, or effects, on then what you do is send them to a bus track, and put the effect on that instead - just the once. You can send any amount of tracks to that, and this way you can keep them on separate tracks and not piled up on top of each other. Creating a bus track is easy; Multitrack menu>Tracks>Add Mono (or Stereo) bus. Then in the output selection for all the tracks you want to send, select the bus you've created instead of Master. Put the effects you want in the bus track, and they will apply to every track you've sent to it. It's then routed to the Master output. There is a lot more flexibility available as well with buses if you use track sends - you can achieve some really complex routings like that.