The command hidepid is used to prevent users from seeing all processes that do not belong to them, but it doesn't offer the possibility of selecting a specific process. Is it possible to hide only one process on a Linux machine? 
How to hide a specific process?
linux;debian;process
A bit dirty and there is probably a cleaner solution (maybe using SELinux or grsec) but you can hide a process by mounting an empty directory inside of /proc/<pid>.For example something like this :mount -o bind /empty/dir /proc/42will prevent regular users from seeing process 42.They will however see that something is hidden as they will be able to see the mount point.If you want to do this for a service you would have to do this everytime it is started, using its init script or whatever.If you want to hide the pid only from a specific user, you could play with namespaces (maybe using pam_namespace) to have the mount bind done only in the namespace of the target user.