NaCl (4)
I believe the answer is:
salt
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nacl</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for salt that I've seen before include "Mariner; sodium chloride" , "Seasoned sailor" , "Condiment - experienced sailor" , "dry wit" , "Brackish" .)