No-can-do
I believe the answer is:
unable
'no-can-do' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for unable that I've seen before include "Not having the neccessary means" , "Not having sufficient power" , "Impotent" , "Having insufficient strength or ability (to do something)" , "Not strong enough" .)