Secure box with sovereign's rifle (10)

I believe the answer is:

winchester

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'rifle' is the definition.
(I know that Winchester is a type of rifle)

'secure box with sovereign's' is the wordplay.
'secure' becomes 'win' (I've seen this in another clue).
'box with' becomes 'chest' (chest is a kind of box. I am not sure about the 'with' bit.).
'sovereign' becomes 'er' (Abbreviation for Elizabeth Regina).
'win'+'chest'+'er'='WINCHESTER'

Can you help me to learn more?

(Other definitions for winchester that I've seen before include "School" , "Hampshire city" , "Rifle < hard disk" , "Cathedral city - rifle - bottle" , "Gunnery" .)

I've seen this clue in The Times.

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