Boring outside broadcast (7)
I believe the answer is:
tedious
'boring' is the definition.
('tedious' can be a synonym of 'boring')
'outside broadcast' is the wordplay.
'broadcast' is an anagram indicator.
'outside' with letters rearranged gives 'TEDIOUS'.
(Other definitions for tedious that I've seen before include "Tiresome, boring" , "not exciting" , "Wearisome, boring" , "flat" , "Dull as ditchwater" .)