Gloat unfairly over the three that flopped completely (10)
I believe the answer is:
altogether
'completely' is the definition.
('altogether' can be a synonym of 'completely')
'gloat unfairly over the three that flopped' is the wordplay.
'unfairly' indicates an anagram (I've seen this in other clues).
'over' is a charade indicator (letters next to each other).
'that flopped' indicates anagramming the letters (I've seen 'flopping' mean this).
'gloat' with letters rearranged gives 'altog'.
'three' is an anagram of 'ether'.
'altog'+'ether'='ALTOGETHER'
(Other definitions for altogether that I've seen before include "Completely, on the whole" , "Wholly" , "nude in this" , "totally" , "Entirely" .)