Disease-carrying fly (6)
I believe the answer is:
tsetse
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">disease-carrying fly</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 tsetse that I've seen before include "fly across Africa" , "cause of sleepiness?" , "African transmitter" , "flies" , "source of sleeping sickness" .)