Disease of parrots (11)
I believe the answer is:
psittacosis
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">disease of parrots</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 psittacosis that I've seen before include "Disease of birds (especially parrots)" , "Contagious disease of birds" .)