A voice of course (5)
I believe the answer is:
tenor
This clue is a double definition.
'a voice' is the first definition.
(one of the voices in a choir say)
'course' is the second definition.
(I've seen this in another clue)
'of' acts as a link.
(Other definitions for tenor that I've seen before include "Highest male voice" , "Male voice (one of three?)" , "Meaning - male singing voice" , "General drift or meaning" , "Pavarotti, maybe" .)