Big name in ratings (7)
I believe the answer is:
nielsen
'big name in ratings' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nielsen that I've seen before include "Musician" , "Leslie --, Canadian actor" , "Scorer" , "Danish composer, Carl (1865-1931)" , "Carl -, Danish cmpsr." .)