Frail, weak (6)
I believe the answer is:
infirm
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">frail</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">weak</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for infirm that I've seen before include "Not physically strong" , "Physically weak as from old age" , "Sickly" , "Debilitated" , "Feeble from age" .)