Queasy feeling (6)
I believe the answer is:
nausea
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">queasy feeling</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 nausea that I've seen before include "A feeling of disgust or illness" , "Squeamishness" , "Unpleasant feeling" , "Feeling of sickness or disgust" , "Condition of feeling imminent sickness" .)