Hilariously funny (7)
I believe the answer is:
riotous
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hilariously funny</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for riotous that I've seen before include "Behaving wildly" , "wild and unruly" , "Rowdy" , "Of mob, disorderly and unruly" , "Wild, uncontrolled" .)