He composed Sweeney Todd ? (6)
I believe the answer is:
barber
'he composed sweeney todd ?' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he composed sweeney' is the wordplay.
'he' becomes 'Bar'.
'composed sweeney' becomes 'ber' (I am not sure about this - if you are sure you should believe this answer much more).
'bar'+'ber'='BARBER'
Can you help me to learn more?
(Other definitions for barber that I've seen before include "Men's hairdresser, musically of Seville" , "Sweeney Todd's occupation in Fleet Street" , "Hair stylist" , "responsible for Hair?" , "who performs on the fringe?" .)