Change euro in new French region (7)
I believe the answer is:
reunion
'french region' is the definition.
(French island in the Indian Ocean)
'change euro in new' is the wordplay.
'change' indicates an anagram.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'euro'+'in'='euroin'
'euroin' is an anagram of 'reunio'.
'reunio'+'n'='REUNION'
(Other definitions for reunion that I've seen before include "Social gathering - French island in the Indian Ocean" , "French island near Mauritius" , "overseas region of France" , "event for ex-students" , "Meeting again after a separation" .)