Uncontrollable fear (5)
I believe the answer is:
panic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">uncontrollable fear</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 panic that I've seen before include "Sudden overpowering anxiety" , "Flap" , "Take fright, lose the head" , "Overwhelming terror" , "Sudden overpowering fear" .)