Endless music in restaurant might be the choice of sommelier (6)
I believe the answer is:
carafe
'the choice of sommelier' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'endless music in restaurant' is the wordplay.
'endless music' becomes 'ra' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'restaurant' becomes 'cafe' (cafe is a kind of restaurant).
'ra' going into 'cafe' is 'CARAFE'.
'might be' is the link.
Can you help me to learn more?
(Other definitions for carafe that I've seen before include "Wine-flask" , "Decanter" , "Table container for wine" , "Wine is decanted into it" , "keeper of wine" .)