Yes! You have to make Moonheart tell you about Mosskit. Then a red X will appear at the beach. Take the mossball in the warriors den and place it on the X. Next moonhigh, Moss-shadow will appear. Click on her to start the dialogue and take her to Bramblestar. If you have at least 80 reputation, he will make you leader right on the spot, if not, earn reputation until you have 80, then Bramblestar will call a clan meeting and make you leader.