The HiSCORE detector, a new non-imaging wide-angle Air-Cherenkov ground based array, is currently in its engineering phase. Time synchronization to nsec-level between detector stations, distributed over 10-100km 2 , is essential to reach best angular resolution for high energy gamma rays. A dedicated time-synchronization and trigger time-stamping system has been developed, and is operating at the Tunka site since October 2012. The system is based on White Rabbit, a new synchronization standard using synchronous Gigabit Ethernet. This first White Rabbit application in a field setup confirms long-term operation with nsec clock precision and phase stability to sub-nsec level; the system is ready for use.