Hi Liftoff
Try this and see if it helps: hold both arms straight out in front of you palms facing each other. Wrap your right hand around your left wrist as if gripping a club. Apply extensor action to your left arm and pull it horizontally across your chest. Notice how the left arm keeps the right from straightening as the right elbow bends.
As a righthander I would prefer to "wrap your left hand around your right wrist" to more emulate the position of the hands on the club -- and surely the point of Extensor Action is to keep the LEFT arm straight -- which the right arm does very easily in this alternate configuration.
But there again I could be mistaken -- as all of this is somewhat new to me