Vessel in which one takes a chum out (4)

I believe the answer is:

pail

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'vessel' is the definition.
(pail is a kind of vessel)

'one takes a chum out' is the wordplay.
'one' becomes 'i' (Roman numeral).
'takes a chum' becomes 'pal' (I can't explain this - if you can you should believe this answer much more).
'out' is an insertion indicator.
'i' put within 'pal' is 'PAIL'.

'in which' is the link.

Can you help me to learn more?

(Other definitions for pail that I've seen before include "Vessel for carrying liquids" , "A bucket as for water" , "A bucket - the kind Jack and Jill used" , "Cylindrical vessel" , "Kind of bucket - ask Jack and Jill" .)

I've seen this clue in the Evening Standard.

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