Apricots not available in sailing troop carriers? That’s a mistake (5)

I believe the answer is:

error

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'that's a mistake' is the definition.
(synonyms)

I don't understand how the rest of the clue works.

(Other definitions for error that I've seen before include "Way of operating" , "heresy" , "Faulty judgement" , "Faulty judgment" , "Miscalculation" .)

I've seen this clue in The Hindu.

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