Railway showing marvellous film (5,7)

I believe the answer is:

great western

'railway' is the definition.
(Great Western Railway is a train company)

'marvellous film' is the wordplay.
'marvellous' becomes 'great' (both can mean very good).
'film' becomes 'western' (Western is an example).
'great'+'western'='GREAT WESTERN'

'showing' acts as a link.

I've seen this clue in The Guardian.

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