"Fetter" is used for a number of different meanings in the Scriptures. In this case, it is basically any of the difficulties that we are creating. So for example, we are sitting in the hall, and all of a sudden we discover that we are angry. Where did this anger come from? What am I thinking about? I'm thinking about my cousin. Why am I angry about my cousin? Because it was his dog that chewed up my bag. Why am I thinking about his dog? Oh, because I heard the dog bark. What was I doing before that? I was mindful of my breath. Oh, so the difficulty of being angry with my cousin came from the ear and hearing the sound. That was the sense contact. I heard the sound of the dog barking, and my mind went off into mental formations, and created my anger, which In that sense is my "fetter". The cause was not being mindful at the hearing. If I would have noted "hearing, hearing", I would never have created a problem. So when they're talking about the "fetters" that arises from the sense doors, that is an example of a "fetter". It is basically a difficulty or a problem that we have created and that originated from missing our mindfulness at the sense contacts.