When organised, Oscar isn't making a pastry treat (9)
I believe the answer is:
croissant
'a pastry treat' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'when organised oscar isn't' is the wordplay.
'when organised' indicates anagramming the letters.
'oscar'+'isnt'='oscarisnt'
'oscarisnt' anagrammed gives 'CROISSANT'.
'making' acts as a link.
Can you help me to learn more?
(Other definitions for croissant that I've seen before include "A rich crescrent-shaped bread roll" , "Continental breakfast crescent" , "French pastry" , "Breakfast roll" , "Breakfast pastry" .)