Bridget Riley's genre (2,3)
I believe the answer is:
op art
'bridget riley's genre' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for op art that I've seen before include "Abstract visual style for the 1960s, giving the illusion of movement" , "Illusory genre" , "It may give the impression of movement" , "Created illusions" , "Illusory graphic style" .)