Previous invention featured in rare broadcast (7)
I believe the answer is:
earlier
'previous' is the definition.
(thesaurus)
'invention featured in rare broadcast' is the wordplay.
'invention' becomes 'lie'.
'featured in' is an insertion indicator.
'broadcast' indicates an anagram.
'rare' anagrammed gives 'earr'.
'lie' placed inside 'earr' is 'EARLIER'.
(Other definitions for earlier that I've seen before include "(Happening) before in time" , "of a bygone age?" , "Nearer the beginning" , "Sooner in time" , "at a previous date" .)