If you advocate something in a dream, your unconscious may be trying to help you make a choice regarding an issue that is affecting you in waking life.
The nature of the thing that you are advocating will affect the meaning of the dream.
For example, if you dream that you advocate donating money to a charity, your unconscious could be telling you that you should avoid being selfish and instead consider how your actions will affect others.
If someone else in your dream is advocating something that you disagree with, you may be experiencing conflicting feelings about an issue in waking life.
A dream that you are acting as an advocate for someone can mean that you feel that you do not receive enough moral support.