Arp's art (4)
I believe the answer is:
dada
'arp's art' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dada that I've seen before include "Art concept" , "Art movement exemplified by Man Ray and Marcel Duchamp" , "Pop" , "Precursor of surrealism" , "artistic trend" .)