This could be a cross stump. It's situated on a natural summit just off the nearby public footpath and there are numerous disused gateposts lying around the area any one of which could have been an accompanying shaft. However if this is a cross base i would have expected it to be a bit more weathered.
Uploaded to Geograph by Jonathan Clitheroe on 16 July 2011
Photo © Jonathan Clitheroe, 16 July 2011. Licensed for reuse under this Creative Commons licence