The voice of an officer to love (4)
I believe the answer is:
alto
'the voice' is the definition.
(alto is a kind of voice)
'an officer to love' is the wordplay.
'an' becomes 'a'.
'officer' becomes 'lt' (I've seen this in other clues).
'to love' becomes 'o' (In tennis, 'love' means 'zero').
'a'+'lt'+'o'='ALTO'
'of' is the link.
(Other definitions for alto that I've seen before include "Woman's singing voice" , "Member of choir" , "One who sings" , "Second of four parts (in singing)" , "Highest male voice: lowest female voice" .)