Show mode off (4)
I believe the answer is:
demo
'show' is the definition.
(I know that show can be written as demo)
'mode off' is the wordplay.
'off' indicates anagramming the letters.
'mode' with letters rearranged gives 'DEMO'.
(Other definitions for demo that I've seen before include "Tape sent to recording studio" , "March (abbr)" , "Protest march (sl.)" , "Protest (abbr)" , "exhibit" .)