The hook grip is a staple of every olympic weightlifter. There isn’t a single movement in olympic lifting that you should NOT use the hook grip for, even deadlifts.
This video can explain much more clearly how to set it up, but it’s basically wrapping your fingers around your thumb, rather than your thumb around your fingers.
If you’re not already using it, give it a try the next time you perform cleans or snatches. It’s a little painful at first – like most things in CrossFit 🙂 – but over time it will improve your lifts.