Crack a joke (4)
I believe the answer is:
jest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">crack a joke</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for jest that I've seen before include "Act in a joking manner" , "fun" , "attempt at humour" , "In ____, playfully" , "Scoff; playfulness" .)