Instrument's voice, even used with acoustic of large venue (7)
I believe the answer is:
ocarina
'instrument's' is the definition.
(ocarina is a kind of instrument)
'of large venue' is the wordplay.
'of' becomes 'o''.
'large venue' becomes 'carina' (I can't explain this - if you can you should give a lot more credence to this answer).
'o'+'carina'='OCARINA'
'voice even used with acoustic' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
(Other definitions for ocarina that I've seen before include "music-maker" , "source of music" , "dated instrument" , "Terracotta wind instrument" , "Simple wind instrument" .)