Crossword Genius

Surprise run on Baltic oil (9)

Ross

I believe the answer is:

lubricant

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'oil' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

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(Other definitions for lubricant that I've seen before include "it has a smoothing effect" , "E.g. oil" , "Eg, grease" , "Substance used to reduce friction" , "Oil or grease" .)

I've seen this clue in the Sydney Morning Herald.
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