Magistrate with right to impound European vessel (6)
I believe the answer is:
beaker
'vessel' is the definition.
(beaker is a kind of vessel)
'magistrate with right to impound european' is the wordplay.
'magistrate' becomes 'beak' (I've seen this before).
'with' means one lot of letters go next to another.
'right' becomes 'r' (common abbreviation).
'to impound' means one lot of letters goes inside another.
'european' becomes 'e' (abbreviation e.g. EU).
'beak'+'r'='beakr'
'beakr' enclosing 'e' is 'BEAKER'.
(Other definitions for beaker that I've seen before include "Large drinking cup" , "Plastic cup without a handle" , "Chemistry lab vessel" , "Mug - large glass" , "Plastic drinking vessel" .)