Close to animal (4)
I believe the answer is:
seal
This clue is a double definition.
'close' is the first definition.
(sealing is a kind of closing)
'to animal' is the second definition.
(I have seen 'Marine animal' mean 'seal' so perhaps 'animal' could also mean 'seal')
(Other definitions for seal that I've seen before include "Settle or decide - say fate" , "Secure; aquatic animal" , "Close tightly - mammal" , "stop leaks" , "Mammal seen swimming" .)