Rattles (8)
I believe the answer is:
unnerves
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rattles</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 unnerves that I've seen before include "Unsettles, disturbs composure" , "Rattles" .)