Childish outburst (7)
I believe the answer is:
tantrum
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">childish outburst</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tantrum that I've seen before include "Child's outburst of bad temper" , "Childish outbreak of temper" , "Burst of temper" , "Childish display of temper" , "Uncontrolled outburst of anger" .)