Looks back and forth (4)
I believe the answer is:
sees
I believe this clue is a double definition.
'looks' is the first definition.
'back and forth' is the second definition.
(Other definitions for sees that I've seen before include "Bishops' dioceses" , "Watches" , "Observes the bishops' domains" , "Clocks" , "Looks (both ways!)" .)