In Google Analytics I have a few websites. I want tracking for only one website.

There are a couple of ways to achieve this. 

1. You can use the ‘invite users’ option. Once you invite another user/email-id then you can give that user/email-id permission for that domain only and the invited user/email-id gets to see leads only for that domain.
2. To remove the websites from Fastbase account you need to remove it from your Google Analytics account. Once you have done that you just need to sync your Google Analytics account with Fastbase account. To sync your Google Analytics account with Fastbase you can do the following:
   1.  In Fastbase WebLeads: click on your profile picture and then click on “Settings” button
   2. scroll down and click “Update profiles”. Once you get a message “Successfully updated your profiles.” Click “OK” and refresh the page.