To flunk upsets Alfie no end! (4)
I believe the answer is:
Here is my best explanation:
'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", "Stop working properly", "Not succeed", "Do not succeed", "Be unable to achieve one's object", "Flunk", "go bankrupt", "Run out; flop", "Go bankrupt" and "Break down".)