Sound process identifying Russian plain (6)
I believe the answer is:
steppe
'russian plain' is the definition.
(I've seen this before)
'sound process' is the wordplay.
'sound' indicates a 'sounds like' (homophone) clue.
'process' becomes 'step'.
'step' sounds like 'STEPPE'.
'identifying' is the link.
(Other definitions for steppe that I've seen before include "crosses Siberia" , "Dry plain of Eurasia" , "Dry grassy plain of eastern Europe and Asia" , "Large treeless area of Siberia" , "(Russian) grassy plain" .)