Gin mixer (5)
I believe the answer is:
tonic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gin mixer</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tonic that I've seen before include "Restorative that invigorates" , "Quinine water" , "something nice and fresh" , "Stimulant" , "Keynote of a scale" .)