Viewers not starting? That's right (3)
I believe the answer is:
yes
'right' is the definition.
(right can mean yes or okay)
'viewers not starting?' is the wordplay.
'viewers' becomes 'eyes' (I've seen this in another clue).
'not starting?' means to remove the first letter.
'eyes' with its initial letter taken away is 'YES'.
'that's' acts as a link.
(Other definitions for yes that I've seen before include "I agree" , "OK" , "Certainly!" , "Confirmation" , "Positive reply" .)