If it has attached a foot hold, it is risky to cut it. But you can move it anywhere you want.
What species is it? My Crocea stopped putting out foot filaments, so it can be moved anywhere. I have, in the past, found a foot left behind, because the clam was not happy where it was. It looks like a white bundle of fleshy fiber about 2-3" x 1".
I would ask in the clam forum for expert opinions/advice as to the proper way to move it if it has a foot hold.