Snare, so revolutionary, shown during one broadcast (5)
I believe the answer is:
noose
'snare' is the definition.
(I know that snare can be written as noose)
'so revolutionary shown during one broadcast' is the wordplay.
'revolutionary' indicates anagramming the letters.
'shown during' means one lot of letters goes inside another.
'broadcast' is an anagram indicator (letters scattered or cast around).
'so' with letters rearranged gives 'os'.
'one' anagrammed gives 'noe'.
'os' placed inside 'noe' is 'NOOSE'.
(Other definitions for noose that I've seen before include "Loop in rope that tightens when pulled" , "Fatal device" , "Catcher" , "Loop in a lariat" , "it could endanger your life" .)