Tartars forsake culture. It's purely aesthetic (3,3,4,4)
I believe the answer is:
art for arts sake
'purely aesthetic' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'tartars forsake culture' is the wordplay.
'tartars forsake' can be anagrammed to 'ART FOR ARTS SAKE'.
Though, I'm not sure how the anagram is indicated.
'it's' is the link.
Can you help me to learn more?
(Other definitions for art for arts sake that I've seen before include "Painter's philosophy" , "painting for the sole benefit of Arthur?" .)