As far as the eye can see (7)
I believe the answer is:
horizon
'as far as the eye can see' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for horizon that I've seen before include "As far as one can see" , "Skyline" , "Line where sky meets sea" , "The line at which the sky and the earth appear to meet" , "Earth/sky interface" .)