Official, say, in European Union rejected one taking flight (7)
I believe the answer is:
refugee
'one taking flight' is the definition.
(someone who has fled)
'official say in european union rejected' is the wordplay.
'official' becomes 'ref' (match official in football, say).
'say' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'in' indicates putting letters inside.
'european union' becomes 'eu'.
'rejected' shows that the letters should be reversed in order.
'eg' going within 'eu' is 'eegu'.
'eegu' backwards is 'ugee'.
'ref'+'ugee'='REFUGEE'
(Other definitions for refugee that I've seen before include "One who seeks asylum abroad" , "Asylum-seeker" , "one seeking shelter" , "Asylum seeker" , "War-forced migrant" .)