Oriental bird is after a sea change (7)
I believe the answer is:
eastern
'oriental' is the definition.
(synonyms)
'bird is after a sea change' is the wordplay.
'bird' becomes 'tern' (tern is a kind of bird).
'is after' says to put letters next to each other.
'change' indicates anagramming the letters.
'sea' with letters rearranged gives 'eas'.
'tern' put after 'eas' is 'EASTERN'.
(Other definitions for eastern that I've seen before include "Facing away from the west" , "towards daybreak?" , "Nearest (anag) - oriental" , "From Japan, say" , "Earnest (anag.)" .)