European moves as October Revolution's beginning (5-5)
I believe the answer is:
serbo-croat
'european' is the definition.
(I've seen this before)
'moves as october revolution's beginning' is the wordplay.
'moves' indicates an anagram.
'beginning' indicates taking the first letters.
The first letter of 'revolutions' is 'r'.
'as'+'october'+'r'='asoctoberr'
'asoctoberr' anagrammed gives 'SERBO-CROAT'.
(Other definitions for serbo-croat that I've seen before include "European" , "language" .)