One of the early stages of setting up the Org Structure is to map Processes against Entities.

Sometimes an Entity or Process is no longer used and can be set to Retired, but in the case that an Entity and a Process Area must remain mapped but only a single process from that area should be unmapped, then ensure that all Audits, Incidents and Key Issues using that Scope are set to Closed.

After all items relying on the Scope are Closed, it will be possible to go to the Map Processes matrix and untick that specific Entity Process.

If you are unable to unmap an Entity Process that you think should be OK to unmap, then please review this article: Ideagen Internal Audit (Aura): Cannot unmap Entity Process or mark Entity (or parent Org Unit) as not Active, even though Entity has no active Audits, Entity Objectives, Incidents, Key Issues, Problems, Audit Findings or Actions