Friend possessing one bucket (4)
I believe the answer is:
pail
'bucket' is the definition.
('pail' can be a synonym of 'bucket')
'friend possessing one' is the wordplay.
'friend' becomes 'pal' (pal is a kind of friend**).
'possessing' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'pal' going around 'i' is 'PAIL'.
(Other definitions for pail that I've seen before include "Milkmaid's bucket?" , "Kind of bucket - ask Jack and Jill" , "Cylindrical vessel" , "water-carrier" , "Open-topped container" .)