Clix Speed / Attack Speed?

[Symmol]

Clix is a system that was added to prevent botting, you get a certain number of clix that decrease every time you click or use a skill, to increase the clix counter you can upgrade Max Clix, and to make the regeneration faster you can upgrade the Clix Speed upgrade.

To answer your question, you need to upgrade Attack Speed in the Click upgrade tab to increase the rate of your click attacks.