Broadcast unfortunate gag (5)
I believe the answer is:
retch
'gag' is the definition.
(I've seen this in other clues)
'broadcast unfortunate' is the wordplay.
'broadcast' shows a homophone (sound like) (how the word might sound on the radio or TV).
'unfortunate' becomes 'wretch' (wretch is a kind of unfortunate).
'wretch' is a homophone of 'RETCH'.
(Other definitions for retch that I've seen before include "Reach" , "Gag, near-vomit" , "Sound and seem to vomit" , "Strain as if to vomit" , "Unsuccessful effort to vomit" .)