The chicken wing is the position at the top of the backswing where the right elbow comes away from the body and the club crosses the target line too soon as a result. It is not limited to just the backswing, you can chicken wing on the follow through as well. The correction is simple but first let's look at what the causes and effects are.
The right elbow becomes disconnected from the body because the left arm rotates counter clockwise in the backswing.
The golf club reverse rotates (clockwise) in the downswing and will open the face and produce a slice or a topped shot due to the left arm pulling away from the body.
To correct this mistake let's understand the function of the right elbow. The right elbow should stay connected (in the same position relative to where it started) and support the club at the top of the swing. Stand at address, simply fold the right arm up 90 degrees and turn your shoulders. From here rotate the left arm "over" the right. On the follow through, do the opposite and rotate the left forearm counterclockwise. This will cause the left arm to extend and fold into the left side. Since the left arm is rotating counterclockwise through impact, the club will be moving faster and the face will be closing producing a longer straighter shot than that old weak slice.