Quick answer: Face-on: at impact the weight is still on the trail foot and the torso leans away from the target; the hips never moved over the lead foot.
What it does to the ball
Low point behind the ball: fat shots, or thins when the wrists rescue it; a high, short flight pushed right.
Root causes (by frequency)
Trying to lift the ball instead of hitting down on it
Fear of moving the head toward the target
A transition with no lateral hip bump
How to fix it
At impact, 80-90% of the pressure should be on the lead foot: finish with your belt buckle facing the target
Drills that fix it
Walk the shot · 10 min · 15 reps
Force full transfer to the lead side Hit the ball and let your trail foot take a full step toward the target after impact, Gary Player style. Taking the step is impossible if the weight hangs back. Do it with an 8-iron at 70% effort.
Frequently asked questions
What is "Hanging back at impact" in the golf swing?
Face-on: at impact the weight is still on the trail foot and the torso leans away from the target; the hips never moved over the lead foot.
What does hanging back at impact do to the ball?
Low point behind the ball: fat shots, or thins when the wrists rescue it; a high, short flight pushed right.
How do you fix hanging back at impact?
At impact, 80-90% of the pressure should be on the lead foot: finish with your belt buckle facing the target
Sources
Titleist Performance Institute — Body-Swing Connection screening