Fish; voice (4)
I believe the answer is:
bass
I believe this clue is a double definition.
'fish' is the first definition.
(I know that bass is a type of percoid)
'voice' is the second definition.
(I know that bass is a type of singing voice)
(Other definitions for bass that I've seen before include "Lowest register of the male voice" , "Fish - low in pitch" , "Fish for the low-voiced" , "part of score" , "Large percussion instrument" .)