It's a bit difficult to fathom this one out. There are several sets of 2 or more stones at the grid ref and slightly southwest that could form part of the arc of a ring cairn and the ground is uneven enough to suggest a low bank in places but nothing definite to my eyes. It's good to read in Idwal's post that even the archaeologists can't agree on some of the sites of the moor.
When I visited in February I thought I could make out a level platform about 6 paces across with 6 very low stones visible on the rim. The area is covered by a mixture of grass and heather and the whole thing is very unconvincing!
The National Monuments Record list a "probable bronze ring cairn (with central cairn) on Gibbet Moor" at SK27894 70557. The NMR report claims it was unrecognised before the RCHME survey 1988-90. It is distinct from the 3 sites in a NW/SE line near SK 27965 70649 which were once interpreted as ringcairns, which Barnatt 1990 interpreted as robbed cairns but which the NMR identifies as Bronze Age house platforms surrounded by field clearance.