Blow it
'blow it' is the definition.
(synonyms)
This is the entire clue.
'blow it' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for fail that I've seen before include "Come to naught" , "Be unable to achieve one's object" , "Don't succeed" , "Be unsuccessful, say in exam" , "Flunk" .)