No way of a pre-view with the clone tool, although it might be a decent suggestion to the Gimp developers.
The clone tool is essentially a brush, you do not see it until you click and paint. Since you seem to be using it as a stamp, two possibilities.
1. Use the clone tool, select a source, make a new layer, clone (paint) on the layer, move the layer. example
https://i.imgur.com/r9mMBYy.mp4
2. Not the clone tool. Make a selection, feathered if needed, copy the selection, paste the selection. This is a temporary layer which can be moved. Anchor the layer. example:
https://i.imgur.com/S2bLA1c.mp4 One advantage of this is you can use an irregular selection. I often use this way for defects on brickwork (removing graffiti etc)
If you use cloning a lot then many operations are assigned (or can be assigned) shortcut keys to speed things up.