Mass of bees (5)
I believe the answer is:
swarm
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mass of bees</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 swarm that I've seen before include "Moving crowd, of bees say" , "Flight of bees" , "Horde" , "Body of bees" , "Go to form new colony" .)