Viewers in theatre yesterday (4)
I believe the answer is:
eyes
'viewers' is the definition.
(I've seen this in another clue)
'in theatre yesterday' is the wordplay.
'in' indicates a hidden word.
'EYES' is hidden in the letters of 'theatre yesterday'.
(Other definitions for eyes that I've seen before include "Looks at carefully" , "(Paradoxical?) film with Cruise and Kidman" , "Peacock's tail markings" , "Views" , "They look" .)