Singer, born idiot (4)
I believe the answer is:
bass
'singer' is the definition.
(I know that bass is a type of singer)
'born idiot' is the wordplay.
'born' becomes 'b' (abbreviation next to the year of someone's birth).
'idiot' becomes 'ass' (both can mean a stupid person).
'b'+'ass'='BASS'
(Other definitions for bass that I've seen before include "part of score" , "Large percussion instrument" , "Fish; deep voice" , "Sea fish; voice" , "Deep-voiced male singer" .)