United Nations article returning Finland to the Finns without dissent (9)
I believe the answer is:
unanimous
'without dissent' is the definition.
(I've seen this before)
'united nations article returning finland to the finns' is the wordplay.
'united nations' becomes 'UN' (abbreviation).
'article' becomes 'an' (English indefinite article).
'returning' says the letters should be written in reverse.
'finland to the finns' becomes 'suomi' (I've seen this in another clue).
'suomi' reversed gives 'imous'.
'un'+'an'+'imous'='UNANIMOUS'
(Other definitions for unanimous that I've seen before include "in complete agreement" , "Without one dissenter" , "Concerted" , "All in agreement, no exceptions" , "no-one disagreeing" .)