Mariner's means of preservation (4)

I believe the answer is:

salt

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'mariner's' is the definition.
(synonyms)

I don't understand the remainder of the clue.

(Other definitions for salt that I've seen before include "Preserve" , "Condiment - experienced sailor" , "NaCl" , "White crystalline substance" , "Brackish" .)

I've seen this clue in the Evening Standard.

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