Out of the question (2,3,2)
(Other definitions for no can do that I've seen before include "That's not possible" , "That's out of the question!" , "Can't manage it, see doc anon" , "Unable to help" , "Bring-a-bottle party?" .)
'out of the question' is the definition.
(synonyms)
This is all the clue.
(Other definitions for impossible that I've seen before include "See 14 down" , "Hopeless" , "See 10" , "Not able to take place" , "Not able to exist" .)