Indecent incident follows outside broadcast (7)
I believe the answer is:
obscene
'indecent' is the definition.
(synonyms)
'incident follows outside broadcast' is the wordplay.
'incident' becomes 'scene' (scene is a kind of incident).
'follows' means one lot of letters go next to another.
'outside broadcast' becomes 'ob'.
'scene' put after 'ob' is 'OBSCENE'.
(Other definitions for obscene that I've seen before include "Shocking" , "Dirty" , "Lewd - offensive" , "Offensive - indecent" , "Repugnant; indecent" .)