snmp view is designed exactly for this.
snmp-server view oneinterface ifEntry.*.1 included
snmp-server view oneinterface ifEntry excluded
snmp-server community mycomm view oneinterface ro
In this example, only ifIndex 1 is allowed. You will have to find out what ifIndex is for your interface. Note that if you reboot the router and didn't configure interface persistance, ifIndex will change and you will have to redo the view again.
HTH