That is not possible (2,3,2)
I believe the answer is:
no can do
'that is not possible' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for no can do that I've seen before include "Informal expression of refusal" , "That's not possible" , "Absolutely not!" , "Bring-a-bottle party?" , "Unable to help" .)