For some reason I am convinced that such a word exists, that I've heard it used in classroom settings, and that I'll recognize it when I see it. But I have no idea what it is. I tried googling this elusive word and failed miserably; I asked a few friends, but they couldn't think of it either. Help!
Suppose someone says: "Well, I don't know much about this topic, and I could be wrong, but XYZ." I feel there's a word to describe the opening that leads into XYZ. It's a sort of hedging: you aren't fully committing yourself; you're worried about being wrong. I can almost hear a high-school teacher saying "Don't start an answer with a _."