It also does it with defrost. It also cause my belt to loosen which causes the squeal. I tighten it and the squeal goes away for a few weeks. Is it the clutch going bad or the whole thing?

Could just be a bad belt or you're not tightening the lock nut on the belt tensioner. Squealing that goes away when the belt is tightened is a problem with the belt. Try a new Continental Elite (formerly Goodyear Gatorback) on it and make sure you tighten the lock-nut and pivot bolts when you've got the belt fully tight and see if that solves the problem.

I agree. Replace that belt and go from there. The AC pump can draw up to 7 hp