21 across
Big
beast
that
was
unsettling
to
nomads
(8)
Big beast that was unsettling to nomads (8)
hints
0
checks
0
hints
The definition is at the beginning of the clue.
How the clue works
Big beast is your definition — that great lumbering prehistoric creature. "Unsettling" is doing duty as the anagram indicator, so take to nomads and shake the letters up, and they'll fall into place as MASTODON.