Patronising — impish (4)
I believe the answer is:
arch
I believe this clue is a double definition.
'patronising' is the first definition.
(I know that patronising can be written as arch)
'impish' is the second definition.
(I've seen this in another clue)
(Other definitions for arch that I've seen before include "in short, is out of date" , "Leading figures" , "Chief - part of foot" , "Knowing, sly" , "Curved masonry construction" .)