Minor earthquake (6)
I believe the answer is:
tremor
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">minor earthquake</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tremor that I've seen before include "Small earthquake" , "Minor earthquake" , "Small vibration" , "Quaver" , "Quivering" .)