Help with tick-based clock

Hello there! I'm currently trying to help my friend make code for a potion tick effect. The basic concept is that every half-second or so, you are randomly sent in a direction. 

This code is attached to a variable that advances by 1 each tick. I tested the movement effect on its own using a right-click function, so I know it's the clock that's broken, and not the movement effect. Any help is appreciated!