Tremble, shudder (5)
I believe the answer is:
shake
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">tremble</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">shudder</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ ></span>
(Other definitions for shake that I've seen before include "Tremble, vibrate" , "Shiver" , "Quiver" , "Tremble; astonish" , "wave" .)