Treat the cause, not the sympton.

Chicken-winging is the body’s natural self protection from what could happen if the the club is approaching the ball at an extremely steep angle. The fear (probably sub conscious) is injury to body parts because of such steep impact. The brain compensates by shortening the lever (the left arm) to try to create contact with the ball, not just mother earth. The solution is to diagnose why the player is coming in so steeply and from the outside and correct the swing fault that is causing the issue. The chicken wing usually self corrects or with some explanation and help the student can mechanically correct.