Supporter of art sale organised around end of June (5)
I believe the answer is:
easel
'supporter of art' is the definition.
'sale organised around end of june' is the wordplay.
'organised' indicates anagramming the letters.
'around' means one lot of letters goes inside another.
'end of' says to take the final letters.
The last letter of 'june' is 'e'.
'sale' is an anagram of 'easl'.
'easl' going around 'e' is 'EASEL'.
(Other definitions for easel that I've seen before include "Van Gogh's stand?" , "Picture support" , "The rest of artists" , "Lease (anag)" , "stand supporting artistic effort" .)