Singer’s theme (5)
I believe the answer is:
tenor
I believe this is a double definition.
'singer's' is the first definition.
(tenor is a kind of singer)
'theme' is the second definition.
(I've seen this before)
(Other definitions for tenor that I've seen before include "Male 17" , "One singing" , "Eg, Caruso" , "General drift or meaning" , "Highest male voice" .)