It's a spring pushing on a tiny little bearing that sits in a hole in the housing, part inside, part outside for click-stopping the turret. If you decide to take things apart, don't lose the bearing! However, if there's dirt inside, coming in through the front isn't the right direction, anyway.
If you decide to clean it by pulling off the eyepiece, which is the right direction if there's crud on the screen inside, you're in for a world of hurt. Or, when you do, and feel the pain, post a note here and I'll make a little tutorial on how to get it all back together right, which is farrrrrrr from obvious. You know how I know. :-(
Hint: there are two prisms and one split tube inside. If you hold the finder nose down (eyepiece up) when you remove the back, and lift the pieces out one at a time, there's a hope you might learn how to put them back. If you just dump them all out on your bench, as I did, good luck.