Note: You will need access to Administration Tools in order to use this feature.
Go to Tools > Advanced Records Management >Split Client and Partner
Select the name of the Partner to be split from the main client from the "Select Partner" box. Once you click on the box, you will have the option to input the partner name and the result will appear in the dropdown.
The Partner record will be separated from the Client record, and you'll end up with two Client records - one for the original Client, and one for the former Partner. You can then do whatever is required to each individual without affecting the other.