Metal mounts for steam engines (4,6)

I believe the answer is:

iron horses

'steam engines' is the definition.
(poetic term for train)

'metal mounts' is the wordplay.
'metal' becomes 'iron' (iron is a kind of metal).
'mounts' becomes 'horses'.
'iron'+'horses'='IRON HORSES'

'for' is the link.

I've seen this clue in the Independent.

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