Layering often works. I found it easiest in shade.
Don't cut the clematis but take a piece about 12" long. Scrape 2 or 3 nodes at the 6" mark and cover it with good soil, or compost. Water well and put a brick or stone on top so it stays damp.
The sun you see in the photo is from the east, not the hot afternoon sun.
Good luck!
