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http://www.flashearth.com/?lat=50.167439&lon=-5.555058&z=18.2&r=0&src=2

It's marked as 'Homestead' on the OS map, and should be visible from Mulfra Hill. A footpath runs N-S just to the east, so I'll try to take a looksee when I'm down there in October.

According to MAGIC, it's
HUT CIRCLES AND ENCLOSURE NE OF TRY FARM
Monument No. CO366
Unfortunately there's no text available.

You could always send a query in via the excellent EH on-line enquiry service or spend a little time searching out via here http://ads.ahds.ac.uk/catalogue/index.cfm?CFID=371014&CFTOKEN=35905756

The MAGIC map has a 'shaft' marked in the middle of the feature. One possibility is that this is a ventilation shaft or auxillary shaft for the nearby Carnaquiddon Mine. It doesn't appear to be a primary shaft as there is no spoil heap or obvious trackway.
Happy hunting