Reminder of broadcast line (3)
I believe the answer is:
cue
'reminder' is the definition.
(I've seen this before)
'broadcast line' is the wordplay.
'broadcast' shows a homophone (sound like) (how the word might sound on the radio or TV).
'line' becomes 'queue' (queue is a kind of line).
'queue' sounds like 'CUE'.
'of' is the link.
(Other definitions for cue that I've seen before include "Hint, prompt" , "Rod used in billiards" , "Actor's prompt" , "line in speech" , "Snooker rod" .)