Musician in small room is close to vocalist (7)
I believe the answer is:
Here is my best explanation:
'musician' is the definition.
(cellist is a kind of musician)
'small room is close to vocalist' is the subsidiary indication.
'small room' becomes 'cell' (I've seen this before).
'close to' suggests the final letters (the \'close\' to the word).
The final letter of 'vocalist' is 't'.
'in' is the link.
(Other definitions for cellist that I've seen before include "Du Pre or Lloyd Weber", "E.g. Casals, du Pre", "Musician in string section", "String player" and "Member of orchestra".)