Insects after drink in drinking vessel (7)
I believe the answer is:
chalice
'drinking vessel' is the definition.
'insects after drink' is the wordplay.
'insects' becomes 'lice' ('louse' can be a synonym of 'insect').
'after' is a charade indicator (letters next to each other).
'drink' becomes 'cha' (cha can mean tea).
'lice' after 'cha' is 'CHALICE'.
'in' is the link.
(Other definitions for chalice that I've seen before include "Church wine cup" , "Large goblet for consecrated wine" , "Eucharistic cup" , "Cup used in church" , "Necessity for communion" .)