Wretched chap, one interrupting news broadcast (5)
I believe the answer is:
swine
'wretched chap' is the definition.
(swine can mean a rotten person)
'one interrupting news broadcast' is the wordplay.
'one' becomes 'i' (Roman numeral).
'interrupting' is an insertion indicator.
'broadcast' indicates anagramming the letters (letters scattered or cast around).
'news' anagrammed gives 'swne'.
'i' placed into 'swne' is 'SWINE'.
(Other definitions for swine that I've seen before include "Pig; unpleasant person" , "Contemptible person; pigs" , "Pig, pigs" , "cad" , "Archaic pigs, Gadarene in Bible" .)