A tune played with levity as a possible result (11)
I believe the answer is:
eventuality
'a possible result' is the definition.
(something which could happen)
'a tune played with levity' is the wordplay.
'played with' indicates anagramming the letters.
'a'+'tune'='atune'
'atune' with its letters mixed up with 'levity' gives 'EVENTUALITY'.
'as' is the link.
(Other definitions for eventuality that I've seen before include "Circumstance" , "Occurrence" , "Contingency" .)