Ostentatiously aesthetic form of tray (4)
I believe the answer is:
arty
'ostentatiously aesthetic' is the definition.
'arty' can be an answer for 'aesthetic' (I've seen this in another clue). I am not sure about the 'ostentatiously' bit.
'form of tray' is the wordplay.
'form of' indicates anagramming the letters (the letters need to be in another 'form').
'tray' is an anagram of 'ARTY'.
Can you help me to learn more?
(Other definitions for arty that I've seen before include "Affectedly unconventional" , "aesthetic pretensions" , "Aesthetically pretentious" , "Having pretensions about paintings, music, etc" , "Having affected interest in visual creativity" .)