Those euros exchanged in treasury (10)
I believe the answer is:
storehouse
'treasury' is the definition.
(thesaurus)
'those euros exchanged' is the wordplay.
'exchanged' indicates anagramming the letters.
'those'+'euros'='thoseeuros'
'thoseeuros' with letters rearranged gives 'STOREHOUSE'.
'in' is the link.
(Other definitions for storehouse that I've seen before include "Depository" , "vault" .)