Appearance of a ghost (13)
I believe the answer is:
manifestation
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">appearance of a ghost</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 manifestation that I've seen before include "Demonstration" , "Symptom (of an ailment)" , "Display" , "Appearance of a ghost" , "Ghostly appearance" .)