Winfrey's production company (5)
I believe the answer is:
harpo
'winfrey's production company' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for harpo that I've seen before include "Silent Marx brother" , "brother who never speaks" , "The dumb Marx brother" , "One of the Marx Brothers" , "The mute Marx Brother" .)