To flunk upsets Alfie no end! (4)
I believe the answer is:
fail
'to flunk' is the definition.
('fail' can be a synonym of 'flunk')
'upsets alfie no end' is the wordplay.
'upsets' indicates an anagram.
'no end' means to remove the last letter.
'alfie' with its final letter taken away is 'alfi'.
'alfi' anagrammed gives 'FAIL'.
(Other definitions for fail that I've seen before include "Go wrong" , "Be unable to achieve one's object" , "Run out; flop" , "Go bankrupt" , "Come to naught" .)