Great composition of Elgar? (5)
I believe the answer is:
large
'great' is the definition.
('large' can be similar in meaning to 'great')
'composition of elgar?' is the wordplay.
'composition of' is an anagram indicator (I've seen this in other clues).
'elgar' with letters rearranged gives 'LARGE'.
(Other definitions for large that I've seen before include "Big, outsize" , "Big, great" , "One has liberty to be at it" , "broad" , "Little's late partner" .)