Relish broadcast of Origin (6)
I believe the answer is:
source
'origin' is the definition.
(I know that origin can be written as source)
'relish broadcast' is the wordplay.
'relish' becomes 'sauce' (relish can mean a sauce or dressing).
'broadcast' shows a homophone (sound like) (how the word might sound on the radio or TV).
'sauce' is a homophone of 'SOURCE'.
'of' is the link.
(Other definitions for source that I've seen before include "Origin; head of stream" , "Fountainhead - journalist's informant" , "Origin; spring" , "From which something springs" , "Beginning to add" .)