US composer’s endless ambition to produce close harmony (10)
I believe the answer is:
barbershop
'harmony' is the definition.
(I've seen this before)
'us composer's endless ambition to produce close' is the wordplay.
I cannot quite understand how this works, but
'composer's' could be 'barbers' (Samuel Barber) and 'barbers' is located in the answer.
The remaining letters 'hop' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for barbershop that I've seen before include "Close four-part harmony for male voices" , "musical style" , "place of high street cuts?" , "Style of music" , "associated with Figaro?" .)