Part of engine splattered with dirt (10)

I believe the answer is:

ingredient

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'part' is the definition.
(I know that ingredient is a type of part)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for ingredient that I've seen before include "Something required for a recipe" , "Component part" , "bit of meal?" , "Constituent" , "Item in a recipe" .)

I've seen this clue in The Times.

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