Intense headache (8)
I believe the answer is:
migraine
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">intense headache</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 migraine that I've seen before include "terrible pain" , "Sick headache" , "misery in capital area" , "A really bad headache" , "Disabling headache" .)