Preserves workers on board (5)

I believe the answer is:

salts

This clue is a double definition.

'preserves' is the first definition.
(salting is a kind of preserving)

'workers on board' is the second definition.
(salt can mean a sailor)

(Other definitions for salts that I've seen before include "Six [EPSOM]'s might revive" , "Old sailors" , "medication" , "Medicinal compounds; Epsom --" , "Saline draughts" .)

I've seen this clue in The Guardian.

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