To revoke access to Klok from your google account please see the following Google Support Article

https://support.google.com/accounts/answer/143031?hl=en&ref_topic=2665423

This would be useful, for example, if you connected Klok to your personal Google account and then wanted to reconnect it to another Google account.

You would first revoke access using the steps in the article above then reopen Klok and connect it to a new Google account.