Behaving badly (6,2)
I believe the answer is:
acting up
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">behaving badly</span>' is the definition.<br/ ><span class="explanation-format__explanation">(acting up is a kind of behaving badly)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for acting up that I've seen before include "Misbehaving" , "Behaving badly" .)