Causing horror (8)
I believe the answer is:
gruesome
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">causing horror</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 gruesome that I've seen before include "Repugnant" , "Go, resume being revolting or gruesome" , "Grisly, horrible" , "'Grisly, macabre (8)'" , "Repulsive, horrid" .)