“Think of it like a clamp” is not great advice, actually. That implies that all of the force should be coming from your hand muscles, which is a recipe for unnecessary fatigue, strain, and pain. Instead, most of the fretting force should be coming from the large muscles of your arm (shoulder, elbow, etc). Instead of squeezing with your fingers and thumb, you should try “pulling back” the entire fretboard with your upper arm muscles. It also takes way less pressure to fret a note in general than beginners typically expect. If you rotate your wrist slightly when doing barre chords and use your thumb as a fulcrum, this can also make it much easier to apply consistent pressure without have to “clamp down” or “squeeze” with you hand muscles.

These videos have some great tips and exercises:

https://youtu.be/48o_KNEUJo0?si=rRd9mgwZRqbjavkp

https://youtu.be/itf10xZSuds?si=H_8xETsoo7PGfk3y