An orphan fills a little metal container (7)

I believe the answer is:

pannier

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'container' is the definition.
(I know that pannier is a type of container)

'an orphan fills a little metal' is the wordplay.
'an orphan' becomes 'annie' (I've seen this before).
'fills' is an insertion indicator.
'a little metal' becomes 'pr' (Pr is an example. I am not sure about the 'little' bit.).
'annie' put inside 'pr' is 'PANNIER'.

Can you help me to learn more?

(Other definitions for pannier that I've seen before include "Bike bag" , "Large basket" , "This will carry" , "Basket on, eg, donkey" , "Carrying basket" .)

I've seen this clue in The Daily Express.

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