Country river, Russian one (5)
I believe the answer is:
rural
'country' is the definition.
(similar in meaning)
'river russian one' is the wordplay.
'river' becomes 'r' (abbreviation for river).
'russian one' becomes 'ural' (I am not sure about this - if you are sure you should believe this answer much more).
'r'+'ural'='RURAL'
(Other definitions for rural that I've seen before include "Characteristic of country life" , "Old country fellow" , "Of the country - pastoral" , "living in the countryside" , "Bucolic; pastoral" .)