Eastern girl: a railway agent (8)
I believe the answer is:
emissary
'agent' is the definition.
(I've seen this before)
'eastern girl a railway' is the wordplay.
'eastern' becomes 'e'.
'girl' becomes 'miss' (I've seen this before**).
'railway' becomes 'ry' (abbreviation for railway).
'e'+'miss'+'a'+'ry'='EMISSARY'
(Other definitions for emissary that I've seen before include "Person sent to negotiate" , "Diplomat sent on special task" , "Agent possibly" , "Person sent on a diplomatic mission" , "Messenger, envoy" .)