Bad dream (9)
I believe the answer is:
nightmare
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bad dream</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 nightmare that I've seen before include "terrible experience" , "Frightening dream" , "Horrifying experience" , "causing distress to the Lord Chancellor?" , "Scary nocturnal fantasy" .)