Valediction from a girl at Brussels (5)
I believe the answer is:
adieu
'valediction' is the definition.
(I have seen 'A valediction' mean 'adieu' so perhaps 'valediction' could also mean 'adieu')
'a girl at brussels' is the wordplay.
'a girl' becomes 'adi' ().
'at' is a charade indicator (letters next to each other).
'brussels' becomes 'EU' (European Parliament is based in Brussels).
'adi'+'eu'='ADIEU'
'from' is the link.
(Other definitions for adieu that I've seen before include "Some say it when leaving" , "Goodbye, monsieur" , "See you later" , "Parting greeting" , "Bye" .)