Musician is beginning to talk with coterie (7)
I believe the answer is:
cellist
'musician' is the definition.
(cellist is a kind of musician)
'is beginning to talk with coterie' is the wordplay.
'beginning to' suggests taking the first letters.
'with' is a charade indicator (letters next to each other).
'coterie' becomes 'cell' (both can mean a group of people).
The first letter of 'talk' is 't'.
'is'+'t'='ist'
'ist' after 'cell' is 'CELLIST'.
(Other definitions for cellist that I've seen before include "Du Pre or Lloyd Weber" , "String player" , "Member of orchestra" , "Lloyd Webber?" , "Musician in string section" .)