Joke, jape (4)
I believe the answer is:
jest
This clue is a double definition.
'joke' is the first definition.
(I know that joke can be written as jest)
'jape' is the second definition.
(I know that jape can be written as jest)
(Other definitions for jest that I've seen before include "Jape, witticism" , "Witty remark" , "it's not serious, so to speak" , "Act in a joking manner" , "attempt at humour" .)