Full Grip In The Clean?

Generally it’s considered ideal to maintain a full grip on the bar through the clean turnover and in the rack position—it can help maintain a better connection in the pull under and reduce bar crashing.
But it’s only a potential advantage… and if you’re not physically capable of doing it, trying to will only make your clean worse.
Mobility is only one part of it—the other part is the proportions of your arm. Significant disparity in upper and lower arm length will prevent a full grip rack position, no matter how mobile you are, or how emphatically your favorite social media personality insists you can do it just like them.
In these cases, trying to maintain a full grip simply slows the turnover and forces you into an insecure rack position, increases the chances of missing cleans, and will likely provide a healthy dose of elbow and wrist pain.
Nothing about an open-hand rack position inherently causes bar crashing or prevents a strong squat position. And again, if you’re anatomically unable to rack a bar properly with a full grip, trying to will be worse.
If you can keep a full or fuller grip, just be sure to not grip the bar tightly as you finish the turnover—gripping tightly will slow the elbows and stop them short. Start relaxing the tension and slide the thumb out of the hook grip as the elbows are coming around in front to ensure a quick, fluid motion into their final position.
If you’re unable to maintain a full grip, now or indefinitely, the goal is essentially the same. Keep a full grip until the elbows are moving up in front of the bar to stay connected well, and then relax the grip to allow the hand to open as much as needed for your elbows to move quickly and completely into the full rack position.
In both cases, you can practice the motion with tall muscle cleans and tall cleans, focusing on the timing that allows a smooth delivery of the bar to the shoulders and maximal security in the rack position. It’s the mechanics of the arms and body overall that determine a good turnover and rack position, not the grip.