It's perfectly safe to turn it off.
The Ericsson Clocksync service was designed on Windows 3.5 and it's purpose was to keep the system times between the clients and server on an even level. This was important for the named pipe connections, RDS and local database updates.
On later versions of Windows (2000, 2003 and XP) the inbuilt time synchronisation services are much better and there is no real need to have the Ericsson Clocksync service running.