Part of macOS
syspolicydGatekeeper
○ Leave it
Checks that apps are from identified developers before they open.
What it is
Runs Gatekeeper, which decides whether an app is allowed to open.
If you stop it
macOS starts it again straight away. Leave it.
The verdict
○ Leave it. Part of macOS, or something that starts again by itself. You never need to close these.
In Activity Monitor
syspolicyd
From Procession’s guide, in the words the app shows.