Farewell now, from yours truly to the EU (5)
I believe the answer is:
adieu
'farewell' is the definition.
(adieu is a kind of farewell)
'now from yours truly to the eu' is the wordplay.
'now' becomes 'ad' (I've seen this in other clues).
'from' means one lot of letters go next to another.
'yours truly' becomes 'i'.
'to the eu' becomes 'eu'.
'ad'+'i'+'eu'='ADIEU'
(Other definitions for adieu that I've seen before include "left, making this?" , "Adios, Arrivederci" , "cheers" , "Goodbye, monsieur" , "Goodbye in France" .)