Broadcast vulgar singer (4)
I believe the answer is:
bass
'singer' is the definition.
(I know that bass is a type of singer)
'broadcast vulgar' is the wordplay.
'broadcast' indicates a 'sounds like' (homophone) clue (how the word might sound on the radio or TV).
'vulgar' becomes 'base' (base can mean vulgar or crude).
'base' sounds like 'BASS'.
(Other definitions for bass that I've seen before include "Male singer and saltwater fish" , "Fish for the low-voiced" , "Freshwater fish and lowest voice" , "Fish; deep voice" , "A fish, or the lowest pitch in music" .)