At the foot of the panel's sidebar there is a quiet Back to website link — the way out for someone who has finished looking at their services.
For your clients, that link should lead to your website.
Open Agency Partners in the sidebar, find What your clients see, and fill in Your website.
What to put there
Your own address: https://youragency.com. Typing youragency.com is enough — it is saved as https:// for you. A page deeper in your site works too, if you would rather they landed somewhere specific.
Leave it empty and there is no link
That is the better default, not a failure to configure something. Until you fill this in, your clients' sidebar simply has one row fewer.
The alternative would be a link on our site, which is the shop of the company you resell. That link is never shown to a client of yours, with or without your own panel domain.
It works on both addresses
If you have claimed a panel domain of your own, the link is there. If your clients sign in on our address instead, the link is there too, and it still goes to you — a client reading its services is your client either way.
Note
Only http and https addresses are accepted. Anything else is refused when you save, with the field marked, rather than accepted and quietly ignored.
What it does not do
It is a link, nothing more. It does not sign your client out, it does not move anything, and your website never learns who clicked it.