African beasts piped up (4)

I believe the answer is:

gnus

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'african beasts' is the definition.
The definition and answer can be both animals as well as being plural nouns.
Maybe you can see a link between them that I don't see?

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for gnus that I've seen before include "South African antelopes" , "Animals" , "Big game" , "Snug (anag) -- wildebeest" , "Large African antelopes" .)

I've seen this clue in The Telegraph.

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