You can only select "Measures From" and "For (Forward to)," not beats or clocks.

I'm unsure what your exact situation is, but there are workarounds in some (not all) situations, e.g., deleting all but that data, saving it as a separate song, editing it as a separate song (changing the time signature sometimes helps to isolate more of the data in measures), then loading it back into the original song as a Track, etc.

But you may just have to move/shift some of the bleedover manually, i.e., anything falling outside the area you define/select by measures.

Hope this helps.