I think for anything other than what you are saying to be true there would have to be some measurable essence, making a person a person, a soul, that could only exist in one body at a time, and in and of itself be unable to be copied no matter advancements in technology. Meaning that a clone could be made, but it would not have life unless the essence allowing it to run was taken from the original which would cause the original to die.
Essentially, magic.
That is the only way I think, you could say a clone is not a clone.
But what you're really doing is kicking the can down the road and saying the soul is the person not the body they inhabit.