Cheat, turning up with Oscar? I'm unable to carry that off! (2,3,2)
I believe the answer is:
no can do
'i'm unable to carry that off' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'cheat turning up with oscar?' is the wordplay.
'cheat' becomes 'con' (con is a kind of cheat).
'turning up' is a reversal indicator.
'with' becomes 'and'.
'oscar?' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'con' back-to-front is 'noc'.
'noc'+'and'+'o'='NO CAN DO'
Can you help me to learn more?
(Other definitions for no can do that I've seen before include "That's out of the question!" , "That's not possible" , "Bring-a-bottle party?" , "Absolutely not!" , "Nothing manageable" .)