Four: Prefix (5)
I believe the answer is:
tetra
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">four prefix</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tetra that I've seen before include "starter for four" , "Small bright fish" , "Bright tropical fish" , "Wrongful act (Law)" , "Denoting four (prefix)" .)