Sometimes, in an effort to clear the hips in the downswing when striking your irons, the spine leans away from the target excessively. This will often lead to either fat or thin shots when the clubhead reaches the ball before the butt end of the club.
As TG Elite Pro Gareth Johnston explains in this golf video tip, the club needs to strike the ball with the shaft leaning forwards. A great way to achieve this is to feel that the lead shoulder moves over the lead foot at impact. This naturally shifts your weight onto your left side for better compression of the ball on your iron shots and increased carry distance.