Last order for sailor (4)
I believe the answer is:
salt
'for sailor' is the definition.
(salt is a kind of sailor)
'last order' is the wordplay.
'order' indicates an anagram.
'last' with letters rearranged gives 'SALT'.
(Other definitions for salt that I've seen before include "NaCl" , "Sea dog" , "Crystalline substance for the table" , "Seasoning; old sailor" , "A defence against ice" .)