Muscle weakness (7)
I believe the answer is:
paresis
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">muscle weakness</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that paresis is a type of muscle weakness)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for paresis that I've seen before include "Sort of weakness" , "Diminished activity of function" , "Weak condition" .)