Condiment for Jack Tar (4)
I believe the answer is:
salt
I believe this is a triple definition!
'condiment' is the first definition.
(I know that salt is a condiment)
'for jack' is the second definition.
(thesaurus)
'tar' is the third definition.
(synonyms)
(Other definitions for salt that I've seen before include "Common substance" , "Seasoning; old sailor" , "Preservative" , "Condiment - old sailor" , "Condiment - experienced sailor" .)