In broadcast completely understand the Vatican (4,3)
I believe the answer is:
holy see
'vatican' is the definition.
(I've seen this before)
'in broadcast completely understand' is the wordplay.
'in broadcast' indicates a 'sounds like' (homophone) clue.
'completely' becomes 'wholly' (synonyms).
'understand' becomes 'see' (synonyms).
'wholly' sounds like 'holy'.
'holy'+'see'='HOLY SEE'
'the' is the link.
(Other definitions for holy see that I've seen before include "Papal office" , "The Vatican" , "Pope's bishopric" , "Central administration of the Roman Catholic religion" , "palace in Rome" .)