Mock or jest (4)
I believe the answer is:
jape
This clue is a double definition.
'mock' is the first definition.
(I've seen this in another clue)
'jest' is the second definition.
(synonyms)
(Other definitions for jape that I've seen before include "Trick or prank" , "Trick - joke - jest" , "Jolly wheeze" , "Kid" , "Lark" .)