@alhaunts The way to sync time in pfsense is ntp.. You don't have to provide time services to anyone else. Ntp is both a client and a server..
There is no setting for like sntp that I am aware.. If you want pfsense time to be correct, you would setup ntp.. By default it just points to pool out on the internet provided by ntp.org
If you want to make sure none of your clients sync to it - then just set the listen interface to localhost only.