It's not bubbly in large heavy bottles (4)
I believe the answer is:
flat
'it's not bubbly' is the definition.
(I know this)
'large heavy bottles' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'heavy' becomes 'fat' (similar in meaning).
'bottles' indicates putting letters inside (bottle can mean to contain).
'l' going within 'fat' is 'FLAT'.
'in' is the link.
(Other definitions for flat that I've seen before include "Boring - apartment" , "Dull; set of rooms" , "Personal residence" , "Not sloping; apartment" , "In music, below the correct pitch" .)