Knowing, superior (4)
I believe the answer is:
arch
I believe this clue is a double definition.
'knowing' is the first definition.
(I've seen this before)
'superior' is the second definition.
(similar in meaning)
(Other definitions for arch that I've seen before include "Bend into upward curve" , "Roguish, cunning" , "Curve of a bridge" , "Curved part of stone bridge, perhaps" , "Mysterious - curve" .)