Confiscates one thousand sterling (8)

I believe the answer is:

impounds

I'm a little stuck... Click here to teach me more about this clue!

'confiscates' is the definition.
('impound' can be a synonym of 'confiscate')

'one thousand sterling' is the wordplay.
'one' becomes 'i' (Roman numeral).
'thousand' becomes 'M' (Roman numeral for a thousand).
'sterling' becomes 'pounds' (I can't justify this - if you can you should give a lot more credence to this answer).
'i'+'m'+'pounds'='IMPOUNDS'

Can you help me to learn more?

(Another definition for impounds that I've seen is " Takes into legal custody, like stray horse".)

I've seen this clue in The Globe and Mail.

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