In poor health (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">in poor health</span>' is the definition.<br/ ><span class="explanation-format__explanation">(an ailing person is unwell)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ailing that I've seen before include "Unwell, in poor condition" , "Infertile" , "In poor health" , "Suffering" , "not doing very well" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">in poor health</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 sickly that I've seen before include "Given often to poor health" , "Prone to illness" , "Feeble; infirm" , "Looking unwell" , "Poorly" .)