European held in a vault (4)
I believe the answer is:
pole
I believe this clue is a double definition.
'european' is the first definition.
(someone from Poland)
'a vault' is the second definition.
(thesaurus)
'held in' acts as a link.
(Other definitions for pole that I've seen before include "support" , "National from east" , "Chopin, for example" , "'Round rod, of wood say (4)'" , "Wooden rod" .)