Rapid escape, an extraordinary vanishing act (13)
I believe the answer is:
disappearance
'vanishing act' is the definition.
(an act of disappearing)
'rapid escape an extraordinary' is the wordplay.
'extraordinary' indicates anagramming the letters.
'rapid'+'escape'+'an'='rapidescapean'
'rapidescapean' is an anagram of 'DISAPPEARANCE'.
(Other definitions for disappearance that I've seen before include "Vanishing act" , "Act of becoming invisible" , "Departure from view" , "Exit (maybe into thin air)" , "fading" .)