Computer infection (5)
I believe the answer is:
virus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">computer infection</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 virus that I've seen before include "Ultramicroscopic infectious agent" , "Transmitted cause of infection" , "Hidden destructive code in computer program - makes you sick" , "Submicroscopic organism, cause of disease" , "Hidden destructive code in a computer program, or cause of illness" .)