Tub or the box containing article, overturned (3)
I believe the answer is:
vat
'tub' is the definition.
(I know that tub can be written as vat)
'the box containing article overturned' is the wordplay.
'the box' becomes 'tv'.
'containing' is an insertion indicator.
'article' becomes 'a' (English indefinite article).
'overturned' says the letters should be written in reverse.
'tv' going around 'a' is 'tav'.
'tav' reversed gives 'VAT'.
'or' acts as a link.
(Other definitions for vat that I've seen before include "Large barrel" , "Large tank or vessel" , "Large tank for liquids, or kind of tax" , "possible source of liquid" , "Fermentation vessel" .)