Ah, I just saw the original, now-closed thread in which @hifitodd said the Clear’s too wobbly. I’m not sure there’s an easy or satisfactory solution to the lack of clamping force, as others have mentioned above. Do not risk voiding your warranty, and beware of damaging the headband. Do not try to bend it. The replacement parts for Focal can be eye-wateringly expensive.
If you absolutely adore the sound of your Clear and couldn’t live without it, here’s an idea inspired by @generic’s suggestion about taking out the hinge pins and installing a new headband: you could see if you can find a cheap, broken pair of Focal Elex/Elear/Clear headphones on sale “for parts only” (there’s a broken Elex on eBay here, but it’s already got a bidder at $99, alas), and then see if you could experiment with bending the broken one’s headband and, if this works, then swap out the headband on your Clear. This assumes the headbands are interchangeable: I don’t know if that’s accurate.
Again, do not do anything that would void the warranty; I’m afraid your best bet might be to return the Clear and find an alternative headphone. I’ll let others chime in here but I suspect a ZMF headphone might be a good option for you, either the Aeolus or the Auteur, depending on your preferences (I see you’ve had a lot of experience with the HD600/650).
I’m sorry the clamp force has been an issue for you.