See this on fixing the problem
You hear the cue to stay over the bar in the snatch and clean, but you’re not sure what that means, and you may even find yourself bewildered by the fact that every elite lifter in the world is behind the bar at the top of the pull. Let’s clear up the confusion, because it’s actually really simple.
Staying over the bar simply means keeping the shoulders above or in front of the barbell in the first pull. Typically we want the shoulder joint approximately above the bar until about the knee, and slightly in front of the bar between the knee and mid-thigh.
The purpose of this position is to help maintain balance and bar proximity while moving us into an optimal position for the final upward explosion of the second pull. That position is balanced over the whole foot, the shins approaching vertical, and the shoulders at least slightly in front of the bar.
This position allows maximal hip extension force and a natural scoop of the knees forward under the bar to allow vertical leg drive to contribute to bar elevation and proper trajectory. Note that the actual position and timing will vary based on proportions and relative hip and leg dominance.
Allowing the shoulders to move behind the bar early—that is, not staying over the bar long enough—reduces possible hip extension force, begins shifting the balance backward, and prevents complete extension of the body in the second pull—the body can’t complete the extension for maximal force and elevation because to do so would place the center of mass so far behind the base that we would fall over. This means a weaker, incomplete pull and usually a jump backward away from the bar, particularly of the feet if not the entire body.
The shoulders do and must move behind the bar at the top of the pull. A proper finish position will place the extended legs approximately vertical with the hips somewhat hyperextended to bring the shoulders slightly behind the hips with the bar in full contact with the body. Reaching this position has nothing to do with staying over the bar or not—this is a different phase of the pull.
Staying over the bar is achieved by simply not opening the hips until the bar is approaching mid-thigh and we’re intentionally initiating the second pull. In other words, we’re trying to stand from the starting position to the second pull entry position without significantly changing the angle of the back. Just push against the ground with the legs and maintain balance while actively pushing the bar back toward the legs.
To train the skill and strength to stay over properly, use halting deadlifts to mid-thigh, segment pulls with pauses at the knee and mid-thigh, short pulls, segment snatches or cleans with a pause at mid-thigh, slow-pull snatches or cleans, and complexes combining any of these exercises with a snatch or clean.