One ends period at home by a hill (10)

I believe the answer is:

terminator

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'one' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

'ends period at home by a hill' is the wordplay.
'ends period' becomes 'term' (I can't explain this - if you can you should believe this answer much more).
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'by' says to put letters next to each other.
'hill' becomes 'tor' (tor is a kind of hill).
'term'+'in'+'a'+'tor'='TERMINATOR'

Can you help me to learn more?

(Another definition for terminator that I've seen is " satellite line".)

I've seen this clue in The Guardian.

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