"Ain't gonna happen!" (4)
'ain't gonna happen' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nohow that I've seen before include "Under no circumstances (as Tweedledum said)" , "Definitely not" , "Absolutely not in America" , "Not by any means, informally" , "Not at all in US" .)
(Other definitions for asif that I've seen before include "Common name in Pakistan" , "I very much doubt it!" , "yeah, right!" .)