To dream of being the understudy in a play or production is a sign that you are the only one standing in the way of a possible successful future. There is an implication that you may need to grow in confidence and put yourself out there a little more to achieve your ultimate success.
To dream of being an understudy suggests that you aren’t being true to yourself. You might be copying others instead of following your own values, and/or being dishonest with the people around you. You won’t achieve the respect you crave until you can learn to be yourself, be truthful, and not knock down others to make yourself look good. However, if you dream of an understudy taking over the part you were supposed to play, this warns of a false friend coming into your life.