Marconi broadcast on sound system is far-reaching (9)
I believe the answer is:
panoramic
'far-reaching' is the definition.
(thesaurus)
'marconi broadcast on sound system' is the wordplay.
'broadcast' indicates an anagram (letters scattered or cast around).
'on' is a charade indicator (letters next to each other).
'sound system' becomes 'PA' (public address system).
'marconi' anagrammed gives 'noramic'.
'noramic' put after 'pa' is 'PANORAMIC'.
'is' is the link.
(Other definitions for panoramic that I've seen before include "Comprehensive" , "All-embracing" , "not restricted" , "giving full view" , "Sweeping" .)