Be unwell (3)
I believe the answer is:
ail
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">be unwell</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ail that I've seen before include "Be in poor health" , "Be unwell, suffer" , "Trouble, afflict; be sickly" , "Worry" , "pain" .)