Lets take example of Clone Contact.

First we need to create n:1 relationship on Contact record:

Then we need to configure mappings:

Now let us put this field on the form navigation and lookup on Contact form:

Once you click Add New on Cloned contacts:

You see, all fields are copied which were configured. Fill and save:

Notice that source contact record is traceable through lookup(above the map). Happy cloning and hope it helps!