From “The Ancient Stones of Wales” by Chris Barber and John Godfrey Williams (1989 Blorenge Books):
“Maen Llwyd, a standing stone that stood in a field on the side of a trackway leading from a place called Maen Llwyd to Parsonage Farm (SO344156). It is marked as Maen Llwyd on the one inch Ordnance Survey map of 1831 and on the Ordnance Survey 1:25000 scale map of 1856.”
There is no sign of the stone on current OS maps, nor is it mentioned on Coflein.