Tube through Liverpool’s opening (4)
I believe the answer is:
vial
'tube' is the definition.
(tubular or cylindrical container)
'through liverpool's opening' is the wordplay.
'through' becomes 'via' (via means going through).
'opening' suggests taking the first letters.
The initial letter of 'liverpools' is 'l'.
'via'+'l'='VIAL'
(Other definitions for vial that I've seen before include "Ampoule" , "Small glass container" , "Small bottle used for medicines, laboratory work, etc" , "Bottle that contains a drug" , "Small container for liquids" .)