Farther than (6)
I believe the answer is:
beyond
'farther than' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for beyond that I've seen before include "Further than or outside the scope of" , "Past" , "Farther along in space, time or degree" , "Farther than or outside" , "On the farther side - in addition" .)