Expression of shock (4)
(Other definitions for gape that I've seen before include "Yawn" , "Stare with open mouth in wonder" , "Appear amazed" , "Look open-mouthed" , "Look in amazement or stupidity" .)
(Other definitions for how that I've seen before include "Who (anag.)" , "In what manner or method?" , "In what way?" , "By what means?" , "See 16" .)