Group of species (5)
I believe the answer is:
genus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">group of species</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for genus that I've seen before include "Biological group containing one or more species" , "Taxonomic group (biol.)" , "Latin class?" , "group of organisms" , "Category above species (Biology)" .)