from details published in the mid-1880s. The Superintendents Registrars District of Donnybrook had not been split at that time, but appears to include the area covers by both 1 and 2 in later years.
Annefield, Donnybrook (town), Priesthouse, Simmonscourt
Clonskeagh, Ballsbridge, Roebuck (part)
Sandymount, Irishtown, Beggars Bush, Ringsend
Fortyacres, Baggotrath, South Wall
Large list of roads/streets in Pembroke Urban District within the townlands listed above
I think your best bet is possibly a mishearing or misunderstanding by the registrar of Claremont Road... which is right next to Sandymount village, and is listed in this district. It would be very strange for there to be no mention of the St.Clare's Park address in something over the years (maps, Thom's directories, voters registers etc.. ) unless it only had this name for a very short period and was quickly renamed.
Shane