Rod-shaped bacterium (8)
I believe the answer is:
bacillus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rod-shaped bacterium</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for bacillus that I've seen before include "CIA bulls, oddly, have a kind of germ" , "Type of bacterium" , "Rod-like bacterium, may cause disease" , "Rod-like bacterium found in lilac bus" , "Single-cell organism, can cause illness" .)