Topical broadcast concerning sight (7)
I believe the answer is:
optical
'concerning sight' is the definition.
(relating to sight)
'topical broadcast' is the wordplay.
'broadcast' is an anagram indicator (letters scattered or cast around).
'topical' with letters rearranged gives 'OPTICAL'.
(Other definitions for optical that I've seen before include "connected to light" , "Involving light" , "Coal tip (anag)" , "Capitol (anag.)" , "Visual" .)