I had a root round for this one but there's not much to see (assuming that the site is accurately marked on the OS 1:25000 map) There does seem to be a semi-circular feature to the west of the fence that it evident by the growth of heather more than anything else and a slight change in the vegetation to the north and south where the track beside the fence passes through the cairn. Might be worth a look for the bank in winter.
There is a legend of a great battle being fought on Broomhead Moor. The nearby Canyard Hills is said by some to mean "The Hills Of The Soldiers" There is also a valley near here called Dwarriden. Taken to mean "The Valley Of The Dwarves". With the legend of the battle in mind, it could make sense of the Bar Dyke.