Shake, shiver (7)
I believe the answer is:
tremble
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">shake</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(trembling is a kind of shaking)</span><br/ ><br/ >'<span class="explanation-format__original">shiver</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for tremble that I've seen before include "Look nervous" , "Quake in one's shoes" , "Betray nerves" , "get the shakes" , "sign of nerves" .)