Grovetown station was opened, in November 1875 right on this flat piece of ground at the published coordinates. It was closed in October 1968. Grovetown itself was named after a large stand (grove) of native bush nearby, known as Big Bush. That stand has mostly been converted to farmland although some still remains and is being restored at the lagoon. I can't tell you any more about this place - all my references mention Grovetown, but say nothing about it.
The cache is 173m away from the published coordinates, at 353 degrees true north. Or 173 metres away, along the cycle track towards Picton - whichever you prefer. By now you should know what to look for!
Excellent parking is available on the other side of the side road, at the Community Hall.
References:
Scoble, J: "Names & Opening & Closing Dates of Railway Stations", published by the Rail Heritage Trust of New Zealand, 2010
Supporting the GeoKids program - my caches have treasure, makes them fun for kids to find!