Can they prevent access to animals? (5)

I believe the answer is:

seals

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'animals?' is the definition.
The definition and answer can be both animals as well as being plural nouns.
Maybe there's a link between them I don't understand?

I don't understand the remainder of the clue.

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(Other definitions for seals that I've seen before include "Fastens or closes securely" , "Marine mammals" , "they're impressive" , "They make an impression" , "Makes waterproof" .)

I've seen this clue in the Evening Standard.

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