Its used for defense if your opponent comes into range and can hit you there a few ways of stopping that from happening beating him to the punch, slip it(dodge), move out of the with your feet, or clinch so he cant throw anything. Ali did it very well with foreman because foreman punch immensly hard instead of wasting energy all the time trying to move and slip the shots he clinched so foreman couldnt throw anything

It probably just stops the other fighters momentum. If a boxer feels like he is in danger of taking a hard hit and has his back against the wall he uses clinching to slow down his opponents momentum and give himself a chance to breathe and regroup.

A clinch in boxing is like a momentary break where the punches stop flying and you get time to think

To stop from being knocked down mainly and too catch a breather. Perfect example is Willie Nelson vs Luciano Cuello in the last rounds.

I never really watch boxing, but I"m watching the Ali vs. Foreman fight right now. I wrestle and done some MMA so I know what a clinch does there, but what's the point of it in boxing? I mean, the ref just separates the boxers.