"I've got a tough act to follow"

In this quote, Scott Caan is acknowledging the difficulty he deals with in attempting to live up to another person's success or reputation. He is basically stating that the person who came before him has actually set a high requirement and it will be tough for him to match or surpass it. This could be in reference to a previous role he played, a relative's achievements, and even a mentor's achievements. By saying he has a "hard act to follow," Caan is acknowledging the pressure and expectations that featured trying to follow in another person's steps. It shows humility and an acknowledgment of the hard work and skill of those who came before him.