Cook in old train oil? (5)

I believe the answer is:

broil

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'cook' is the definition.
(I've seen this in another clue)

'old train oil?' is the wordplay.
'old train' becomes 'br' (I can't explain this - if you can you should believe this answer much more).
'br'+'oil'='BROIL'

'in' is the link.

Can you help me to learn more?

(Other definitions for broil that I've seen before include "stew" , "cook?" , "American heat" , "disturbance" , "overheat?" .)

I've seen this clue in the Evening Standard.

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