Failed to take down broadcast (4)
I believe the answer is:
blew
'failed' is the definition.
(blowing is a kind of failing)
'down broadcast' is the wordplay.
'down' becomes 'blue' (both can mean sad).
'broadcast' indicates a 'sounds like' (homophone) clue (how the word might sound on the radio or TV).
'blue' is a homophone of 'BLEW'.
'to take' acts as a link.
(Other definitions for blew that I've seen before include "Squandered" , "Breathed hard" , "Sounded (a whistle)" , "Squander in the past" , "Tooted" .)