Heard abject singing voice (4)
I believe the answer is:
bass
'singing voice' is the definition.
(I know that bass is a type of singing voice)
'heard abject' is the wordplay.
'heard' indicates a 'sounds like' (homophone) clue.
'abject' becomes 'base' (synonyms).
'base' is a homophone of 'BASS'.
(Other definitions for bass that I've seen before include "A fish, or the lowest pitch in music" , "deep in the sound" , "Freshwater fish and lowest voice" , "Very low - perch" , "Fish - low in pitch" .)