Fall ill again (7)
I believe the answer is:
relapse
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fall ill again</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for relapse that I've seen before include "Worsen" , "Return to sickness" , "Fail to maintain progress" , "Pleaser may slip to earlier state" , "Regress, fall back" .)