Shuts up the animals (5)
I believe the answer is:
seals
'shuts' is the definition.
(sealing is a kind of shutting)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for seals that I've seen before include "Makes waterproof" , "Great swimmers" , "they're impressive" , "Fastens or closes securely" , "They make an impression" .)