The horizon is this, to the best of my understanding (2,3,2,1,3,3)
I believe the answer is:
as far as i can see
'to the best of my understanding' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for as far as i can see that I've seen before include "The faintest star is" , "To the best of my understanding" , "to my knowledge" .)