Abound, swarm with (4)
I believe the answer is:
teem
I believe this clue is a double definition.
'abound' is the first definition.
(I've seen this before)
'swarm with' is the second definition.
(thesaurus)
(Other definitions for teem that I've seen before include "Seethe" , "(Of rain) pour down" , "Rain cats and dogs" , "Rain buckets" , "Be swarming (with)" .)