Most likely the return spring either broke or came off of the passenger side of the release arm. Get under it and listen at both sides of the bell housing while someone presses the clutch. If it's louder on the passenger side, that's definitely what it is. The spring holds that end of the release arm against the ball joint. What you're hearing is the arm striking the ball joint when you press the clutch. Probably not worth pulling the transmission to fix it unless it really bothers you. Here's a pic.