Irrational fear (6)
I believe the answer is:
phobia
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">irrational fear</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for phobia that I've seen before include "Pathological fear" , "Obsessive and persistent fear of something" , "Great fear of something" , "A lasting abnormal fear of something" , "Aversion" .)