A drawback to Oscar, for instance (5)
I believe the answer is:
award
'instance' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'a drawback to oscar' is the wordplay.
'drawback' says the letters should be written backwards.
'to oscar' becomes 'draw' (I can't justify this - if you can you should believe this answer much more).
'draw' back-to-front is 'ward'.
'a'+'ward'='AWARD'
'for' is the link.
Can you help me to learn more?
(Other definitions for award that I've seen before include "settlement" , "Tony, say" , "Bestow" , "Give officially as prize or payment" , "Tony, for example" .)