Jack and Jill's vessel (4)
I believe the answer is:
pail
'jack and jill's vessel' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pail that I've seen before include "water-carrier" , "A bucket - the kind Jack and Jill used" , "Kind of bucket - ask Jack and Jill" , "Container; sounds like dim" , "Open-topped container" .)