Peak viewing period (5,4)
I believe the answer is:
prime time
'peak viewing period' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for prime time that I've seen before include "For monks perhaps around dawn" , "Peak viewing period" , "when most people are turned on" , "When viewing figures are highest" , "Optimum period for broadcasters" .)