Trans-Siberian Railroad city (4)
I believe the answer is:
omsk
'trans-siberian railroad city' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for omsk that I've seen before include "City of south central Russia" , "City in Siberia" , "Russian place" , "City of Asian Russia" , "Womble" .)