Salty water (5)
I believe the answer is:
brine
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">salty water</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for brine that I've seen before include "Salted water" , "pickle" , "Seawater" , "Solution of salt in water" , "preservative" .)