Though in most places in Orkney water levels have risen, the first O.S. shows this site as a seperate islet. Perhaps the topographic details of the 1882 map came from a particularly wet time ? The isthmus is matched by many Orcadian sites recorded as being connected by causeways or stepping stones. A few of these have been claimed as crannogs, an exception being the Loch of Wasdale's comparison to the causewayed island duns of the Western Isles. You must tread carefully in more senses than the literal ;-)
Don't try and reach it by going around the shore from Via (unless you ave some serious welligogs, when you might just).
RCAHMS NMRS record no. HY21NE 1 at HY25171649 though much destroyed and built over this stony mound is the remains of a 65' diameter broch on an islet in the Loch of Clumly that lies opposite Via, linked to the shore by a marshy stretch occasionally over-run by the waters. A bit of broch-type wall on the NW has now gone to leave us with the only exposed area a 12m stretch of outer wall-face 0.7m high on the SW of this 2m high mound and outbuilding traces beneath tumble just outside this. There is a likely-looking cell just within the western end of the wall.