I have clematis that keep on keeping on too! I cut my prolific flowerers back down to a foot or so above the ground a couple of months ago, and didn't expect anything to happen until next year but they've gone the extra mile for me and I have a solitary flower on one and several on another. The other 5 have growth but are a little less forgiving! Your bloom is a stunner!
Finally after 5 years of clematis wilt killing this right back to the root before it grew more than 2 feet, it has finally decided to make it onto the wires I put up to train it! What causes clematis wilt and why has it suddenly stopped??! Can't wait for a second bloom so I can identify it 🌸
It is cause by a fungus called Phoma clematidina probably. If you see any leaves starting to gp brownish cut the stem back to a healthy non marked part of the stem. You should also clean or disinfect secateurs after as the spores from the fungi to stop the spores going anywhere else @david