Go out live: revolutionary start for broadcast (3)
I believe the answer is:
ebb
'go out' is the definition.
(as in the tide going out)
'live revolutionary start for broadcast' is the wordplay.
'live' becomes 'be' (synonyms).
'revolutionary' says the letters should be written in reverse (letters revolve around).
'start for' indicates taking the first letters.
The initial letter of 'broadcast' is 'b'.
'be' in reverse letter order is 'eb'.
'eb'+'b'='EBB'
(Other definitions for ebb that I've seen before include "Not to wax" , "Abate" , "recession" , "Flow outwards" , "state of decline" .)