Country girl fills silo (7)

I believe the answer is:

britain

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'country' is the definition.
(Britain is an example)

'girl fills silo' is the wordplay.
'girl' becomes 'Rita' (woman's name).
'fills' means one lot of letters goes inside another.
'silo' becomes 'bin' (I can't justify this - if you can you should believe this answer much more).
'rita' going inside 'bin' is 'BRITAIN'.

Can you help me to learn more?

(Other definitions for britain that I've seen before include "Island north of France" , "Largest UK island" , "Main UK island" , "Monarchy" , "UK's largest island" .)

I've seen this clue in The Guardian.

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