Sleep bruxism, also known as nocturnal tooth grinding, is the medical term for clenching or grinding teeth during sleep.
I suppose I'm not saying anything new, but it's worth a reminder. Most people who grind their teeth at night are unaware of it, so unless you have very obvious symptoms it's hard to know that you have this condition or that it even exists at all. Unfortunately teeth grinding can cause tinnitus, and the more stressed you are, the more you grind your teeth, which in turn worsens your tinnitus.
I went to a dentist and he confirmed that I was a grinder, so I had a mouth guard made, which I got in early August, and after wearing it every day since then, my t has improved a lot. Most of the time I don't notice it, and it's only really bothersome when I'm in complete silence.
I hope that someone can get some relief from this. Good luck and stay strong.