Sir — Elgar, composer (6)
I believe the answer is:
edward
(Other definitions for edward that I've seen before include "Longshanks, e.g." , "The eighth one abdicated" , "Lear, perhaps" , "King who abdicated" , "I (1239-1307), II (1284-1327), III (1312-77), IV (1442-83), V (1470-83?), VI (1537-53), VII (1841-1910) or VIII (1894-1972)" .)