Preserve drink container (6)
I believe the answer is:
jamjar
'container' is the definition.
(jamjar is a kind of container)
'preserve drink' is the wordplay.
'preserve' becomes 'jam' (jam is a kind of preserve).
'drink' becomes 'jar' (colloquial).
'jam'+'jar'='JAMJAR'
(Other definitions for jamjar that I've seen before include "Vessel" , "London Transport?" , "Glass container" , "Container for preserve" , "Container for conserve" .)