Remarkably regal composer (5)
I believe the answer is:
elgar
'composer' is the definition.
(Edward Elgar)
'remarkably regal' is the wordplay.
'remarkably' is an anagram indicator (I've seen this in other clues).
'regal' with letters rearranged gives 'ELGAR'.
(Other definitions for elgar that I've seen before include "He scored" , "Land of Hope and Glory composer" , "Glare critically at the British composer" , "Glare at composer of 'The Dream of Gerontius'" , "The 18 [APOSTLES] creator" .)