I don't see where this would be a viable option to accomplish anything. The concept behind the clone tool is to move a "clone from" marker across a position, and have that exact image cloned at the "clone to" position. Having one of the points stationary would not result in a copying of the original. The only conceivable concept I can fathom is to clone an image in a complete circle about itself.
However, what you are describing sounds like what you do when you reposition the clone brush. In that case you right click on the position where you want to move the new "clone from" location to begin, then once that point is established, the "clone to" position will move freely and independantly until you left-click again. At that point, it will fresse the clone points, and cloning will resume as normal.