When you add group:role permissions to faculty users you will notice a Clinical Faculty checkbox in each organization they are a part of. When you add a user through the user interface this will automatically be checked off. Note that as of Elentra ME1.12 you cannot set a user as a clinical faculty member in one organisation but not another.
This is mostly a tool to store information and is rarely used elsewhere in Elentra. One place it is used is when reporting on annual reporting. When generating reports on annual reports you can filter by clinical and non-clinical faculty (see below).