Crossword Genius

Cream engine, the last on railway (5)

Ross

I believe the answer is:

ivory

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'cream' is the definition.
(ivory is a cream colour)

'engine the last on railway' is the wordplay.
'engine' becomes 'ivor' (I have seen 'Online engine' mean 'ivor' so perhaps 'engine' could also mean 'ivor').
'the last on railway' becomes 'y' (I can't explain this - if you can you should believe this answer much more).
'ivor'+'y'='IVORY'

Can you help me to learn more?

(Other definitions for ivory that I've seen before include "Key perhaps" , "recluse's tower?" , "Like the tower" , "Substance in elephant tusks" , "Creamy colour" .)

I've seen this clue in The Times.
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