In the countryside, rook seen by Russian river (5)
I believe the answer is:
rural
'in the countryside' is the definition.
(I've seen this before)
'rook seen by russian river' is the wordplay.
'rook' becomes 'r' (abbreviation in chess).
'seen by' says to put letters next to each other.
'russian river' becomes 'ural' (I've seen this in other clues).
'r'+'ural'='RURAL'
(Other definitions for rural that I've seen before include "Agrestic" , "Countryfied" , "Characteristic of the countryside" , "Of the country - pastoral" , "Countrylike" .)