Holy terror (4)
I believe the answer is:
brat
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">holy terror</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for brat that I've seen before include "Spoilt child" , "Mervyn -- (Titus Groan)" , "Bad child - pack member!" , "Nasty little kid" , "Horrible child" .)