Swarm (with) (4)
I believe the answer is:
teem
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">swarm with</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for teem that I've seen before include "(Of rain) fall heavily" , "Be swarming (with)" , "Flow copiously" , "pelt" , "Seethe" .)