Many golfers struggle with over-swinging the club at the top of the swing. This problem can lead to many other issues later on in the swing. To work on this, it is important not to see it as a club, arm or torso issue, but to look to your legs for the cure.
Put simply, you need to use your legs and pelvis to limit your backswing.
Try and feel like your knees are slightly braced before starting your backswing, as if you are trying to push them further apart.
This should enable you to make better backswings and show far greater clubface and path control, helping to improve the dispersion of your shots.