Trembles with fear (6)
I believe the answer is:
quakes
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">trembles with fear</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 quakes that I've seen before include "Trembles with fear" , "Shivers due to tremors?" .)