Perceive by sight (3)
I believe the answer is:
see
'perceive by sight' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for see that I've seen before include "Understand; watch" , "Chelmsford" , "Perceive; meet (someone)" , "Observe the bishop's domain" , "Observe the bishop's jurisdiction" .)