Broadcast foundation course (5)
I believe the answer is:
route
'course' is the definition.
(I've seen this before)
'broadcast foundation' is the wordplay.
'broadcast' indicates a 'sounds like' (homophone) clue (how the word might sound on the radio or TV).
'foundation' becomes 'root'.
'root' is a homophone of 'ROUTE'.
(Other definitions for route that I've seen before include "Established line of trave" , "Send a particular way" , "' - - 66', Nat Cole song" , "Course of journey" , "Itinerary; way" .)