Right next to river in the countryside (5)
I believe the answer is:
rural
'in the countryside' is the definition.
(rural means in the countryside)
'right next to river' is the wordplay.
'right' becomes 'r' (abbreviation).
'next to' says to put letters next to each other.
'river' becomes 'ural' (Russian river).
'r'+'ural'='RURAL'
(Other definitions for rural that I've seen before include "living in the countryside" , "Rustic" , "Old country fellow" , "Relating to country life" , "Not urban" .)