Garment for Oberon's part (4)
I believe the answer is:
robe
'garment' is the definition.
(robe is a type of garment)
'for oberon's part' is the wordplay.
'part' indicates a hidden word.
'ROBE' is hidden within 'for oberons'.
(Other definitions for robe that I've seen before include "Ceremonial garment, clothe" , "official dress" , "Loose or formal garment" , "judge's garment" , "Old cloak for Boer" .)