Attorney leaves western state for Russian river (4)
I believe the answer is:
neva
'russian river' is the definition.
(river in Russia)
'attorney leaves western state' is the wordplay.
'attorney' becomes 'DA' (district attorney).
'leaves' indicates named letters should be taken away.
'western state' becomes 'nevada' (I've seen this before).
'nevada' with 'da' taken out is 'NEVA'.
'for' acts as a link.
(Other definitions for neva that I've seen before include "St Petersburg river" , "distant river" , "runner in St Petersburg" , "Woman" , "banker in Russia" .)