Close to an 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 an 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 "Fasten securely; aquatic mammal" , "Secure; aquatic animal" , "Aquatic animal - to make an impression" , "Fasten with hot wax" , "Close up - marine mammal" .)