Almost calm, arrive on one African plain (9)

I believe the answer is:

serengeti

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'african plain' is the definition.
(geographic region in Tanzania)

'almost calm arrive on one' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'calm' becomes 'serene' (synonyms).
'arrive' becomes 'get' (synonyms).
'on one' becomes 'i' (Roman numeral. I am not sure about the 'on' bit.).
'serene' with its final letter taken off is 'seren'.
'seren'+'get'+'i'='SERENGETI'

Can you help me to learn more?

(Other definitions for serengeti that I've seen before include "Afr. plain; green site (anag.)" , "Tanzanian national park area" , "area of Tanzania" , "Green ties (anag.)" , "place to watch game" .)

I've seen this clue in The Telegraph.

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