A mammoth beast (8)

I believe the answer is:

mastodon

I believe this is a double definition.

'a mammoth' is the first definition.
(thesaurus)

'beast' is the second definition.
(mastodon is a kind of beast)

(Other definitions for mastodon that I've seen before include "giant from the past" , "Extinct beast" , "Big beast" , "Extinct elephant-like mammal" , "Prehistoric creature" .)

I've seen this clue in The Irish News.

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