Coming “over the top” is easily the average player’s most common fault. From the top of the swing, the most common mistake I see is people initiating the downswing by spinning the shoulders and upper body towards the target. This forces your hands and arms away from your upper body and brings the club to the ball from the outside. Depending on your clubface, the result is either a slice or a pulled shot. This closed stance exercise will counteract the wrong move to help you prevent "coming over the top".
Start in your normal stance.
Pull your back foot (right foot for a right-handed golfer) so that your toe is in line with your front heel.
Make practice swings to feel the arms coming down closer to your body on the downswing.
Start by doing this exercise in slow motion, feel how your hips initiate the movement towards the target and the shoulders and arms follow.
Pick up the pace until you can swing at normal speed.
This drill can be done with or without hitting a ball. This is an isometric exercise that will not only train the proper movement but will tone muscles in the hips, shoulders and chest