Improvise triumph against idiot (4,2)
I believe the answer is:
wing it
'improvise' is the definition.
(I've seen this in another clue)
'triumph against idiot' is the wordplay.
'triumph' becomes 'win' (a win is a victory or triumph).
'against' says to put letters next to each other.
'idiot' becomes 'git'.
'win'+'git'='WING IT'
(Other definitions for wing it that I've seen before include "Perform without any preparation" , "Improvise" .)