Complete your backswing by turning, not collapsing arms
Trying to complete the swing by breaking down its structure can lengthen it, while collapsing the arms is contrasted with continuing the shoulder turn. One described example involved an attempted wrist-hinge motion, followed by wrist cupping and an open clubface. The stated focus is to keep the elbows fairly close together and maintain the starting structure as much as possible.
Channel: Danny Maude
Watch official source at 5:23