Russian ballet's cocktail of sound (5)
I believe the answer is:
kirov
'russian ballet's' is the definition.
(I've seen this before)
'cocktail of sound' is the wordplay.
'cocktail' becomes 'kir' (I've seen this before).
'of' becomes 'o'.
'sound' becomes 'v' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'kir'+'o'+'v'='KIROV'
Can you help me to learn more?
(Other definitions for kirov that I've seen before include "Russian city and ballet company" , "Soviet city" , "Soviet ballet" , "Russian dancers" , "St Petersburg ballet company, founded c. 1740" .)