Final use of salt (4)
I believe the answer is:
last
'final' is the definition.
(synonyms)
'use of salt' is the wordplay.
'use of' indicates an anagram.
'salt' is an anagram of 'LAST'.
(Other definitions for last that I've seen before include "It helps cobbler" , "` `Let the cobbler stick to his ....' '" , "The cobbler's equipment will endure" , "stay at the back" , "nowhere near winning Miss World?" .)