Late-night host who once wrote for "The Simpsons" (6)
I believe the answer is:
obrien
(Other definitions for obrien that I've seen before include "'Kate ..., Edna ..., (1'5)'" , "Kate . . . . . ., Flann . . . . . . (1'5)" , "Edna, novelist" , "Conor Cruise, Edna, Flann or Vincent" , "I be Ron, strangely, with this surname" .)