A great potentate upsets the arts (4)
I believe the answer is:
tsar
'a great potentate' is the definition.
'tsar' can be an answer for 'potentate' (I've seen this before). I'm not sure about the 'a great' bit.
'upsets the arts' is the wordplay.
'upsets' is an anagram indicator.
'arts' is an anagram of 'TSAR'.
Can you help me to learn more?
(Other definitions for tsar that I've seen before include "Absolute ruler" , "Person in charge" , "Russian monarch" , "Alexander and Nicholas held this title in Russia" , "Russian leader" .)