Final sprinkling of salt (4)
'final' is the definition.
'sprinkling of salt' is the wordplay.
'sprinkling of' indicates anagramming the letters (the letters are sprinkled or scattered around).
'salt' is an anagram of 'LAST'.
(Other definitions for last that I've seen before include "Most unlikely", "Form on which a shoe is made", "The cobbler's equipment will endure", "` `Let the cobbler stick to his ....' '", "Continue".)