Perception is visible (7)
I believe the answer is:
insight
This clue is a double definition.
'perception' is the first definition.
(I know that insight is a type of perception)
'visible' is the second definition.
(something in sight is visible)
'is' is the link.
(Other definitions for insight that I've seen before include "Sudden understanding" , "vision" , "Intuition" , "Intuitive understanding" , "Perspicacity" .)