Vat (4)
'vat' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tank that I've seen before include "Car fuel container" , "Vat" , "Combat vehicle" , "Armour-plated military vehicle" , "Possible alternative to barrel" .)
(Other definitions for keg that I've seen before include "Sort of beer" , "What's found at King's Head" , "Barrel as for beer" , "Small cask or barrel" , "Small beer cask" .)
'vat' is the definition.
(synonyms)
This is all the clue.
(Other definitions for tub that I've seen before include "Maybe it sailed" , "Large plant pot" , "Container, usually for washing" , "Kind of bath" , "Small round container" .)