He composed some memorable harmonies (5)
I believe the answer is:
lehar
'he composed' is the definition.
The definition suggests a singular noun which matches the answer.
'some memorable harmonies' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'LEHAR' is hidden in the letters of 'memorable harmonies'.
Can you help me to learn more?
(Other definitions for lehar that I've seen before include "Franz . . . . . composed 'The Merry Widow'" , "Operetta composer" , "Franz -----, composer of The Merry Widow" , "Musician" , "Hungarian composer of operettas" .)