Composer of regal disposition (5)
I believe the answer is:
elgar
'composer' is the definition.
(Edward Elgar)
'regal disposition' is the wordplay.
'disposition' indicates anagramming the letters.
'regal' is an anagram of 'ELGAR'.
'of' is the link.
(Other definitions for elgar that I've seen before include "Enigma Variations composer" , "Sir Edward -, English composer" , "Scorer" , "Glare at great English composer" , "British composer, d. 1934" .)