Containing water (7)
I believe the answer is:
aqueous
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">containing 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 aqueous that I've seen before include "Dissolved in water" , "Watery" , "Holding water" , "flooded with water?" , "Containing water" .)