No, that would not make you his descendant. He has no living descendants. He has ancestors and you may or may not share some of those same ancestors. You would be connected to him or related to him, but not a desendant, although it is quite possible that you could both be descendants of a common ancestor if you trace your tree back far enough and it connects with his tree.

However, I'm not understanding the line of descent that you are describing. How would Florance Clemons be related to Samuel Clemens? What relationship is said to exist between the two of them? I am certain that they are not siblings.