We would like to have an attribute on the Account form called General Practitioner. This attribute would be a filtered lookup of Contacts.
So the lookup is defined as shown below.
But this will create a left navigation link automatically on Contact Form.
So in some cases we may not needed this left navigation link. So whenever we define a lookup its a very good practice to think whether we need the left navigation link.
In this we don't prefer to have the left navigation link Account. So to remove this we need to go to relations.
And find out the relation of the defined lookup. Double click on it.
We have the option to choose ' Do Not Display'. Save the relation and publish.
As you could see the unwanted left navigation is removed.