Finally it's cosy for bees (5)
I believe the answer is:
swarm
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for swarm that I've seen before include "Go to form new colony" , "Dense group (of insects)" , "many insects" , "Climb; cluster of bees" , "Congregate" .)