Singing with US composer’s hard work! (10)
I believe the answer is:
barbershop
'singing with us' is the definition.
I can't tell whether this definition defines the answer.
'composer's hard work' is the wordplay.
'composer's' becomes 'barbers' (Samuel Barber).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'work' becomes 'op' (abbreviation for opus).
'barbers'+'h'+'op'='BARBERSHOP'
Can you help me to learn more?
(Other definitions for barbershop that I've seen before include "place of high street cuts?" , "Style of close-harmony singing" , "Style of music" , "quartet music?" , "Close-harmony music" .)