Prank? Get away without notice (8)
I believe the answer is:
escapade
'prank?' is the definition.
(thesaurus)
'get away without notice' is the wordplay.
'get away' becomes 'escape' ('escape' can be a synonym of 'get away').
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'notice' becomes 'ad'.
'escape' placed around 'ad' is 'ESCAPADE'.
(Other definitions for escapade that I've seen before include "Mischievous exploit" , "Daring stunt" , "Adventurous T [TREAT]" , "Madcap adventure" , "Wild and exciting undertakings" .)