Composer of regal variations (5)
I believe the answer is:
elgar
'composer' is the definition.
(Edward Elgar)
'regal variations' is the wordplay.
'variations' indicates an anagram.
'regal' with letters rearranged gives 'ELGAR'.
'of' is the link.
(Other definitions for elgar that I've seen before include "Sir Edward -, English composer" , "Out of the strange glare comes an English composer" , "13 composer, 1857-1934" , "He scored" , "Glare strangely at the English composer" .)