His symphonies, for instance, are in large form (5)
I believe the answer is:
elgar
'his symphonies for instance are' is the definition.
The definition suggests a singular noun which matches the answer.
'large form' is the wordplay.
'form' indicates anagramming the letters (a different form of the same letters).
'large' is an anagram of 'ELGAR'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for elgar that I've seen before include "Enigma Variations composer" , "Nimrod composer" , "Glare critically at the British composer" , "[NIMROD] 's creator" , "Enigma Vars. composer" .)