Most of you playing Ultimate would've already heard this from one of the senior players on your team, but here we go, anyway: There are only two speeds for cutters in Ultimate, zero and full-speed. This may be a little bit of an exception, but most players who have played for a few months would already realize that handlers don't give you a disk, if you are not cutting at your full speed! But, the speed rule doesn't hold true only when you are cutting. It holds when you are clearing too! You need to be clearing as hard as you cut, and still "remain active" when you are clearing. By active, I mean that you should still be expecting a pass from the handler, and be ready to catch anything that your handlers sends at you. Even if that's not the case, you should atleast make your defender believe that you are active. Otherwise, he/she can poach on you!
I often use the "extent" to which my defender is poaching on me, as an indicator of how active I am on the field. If I'm letting my defender poach on me and get discs going to other players on my team, I'm definitely not being active enough. This can be used as an indicator not just when I'm standing in the (vert/ho) stack and waiting, but also when I'm clearing. When clearing, you should ideally be looking at your handler atleast from the corner of your eye, and keep looking for opportunities of asking for a pass, the moment your defender slackens a little upon you.