Eye drop (4)
I believe the answer is:
tear
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">eye drop?</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 tear that I've seen before include "Secretion of the lacrymal glands" , "A drop of sadness" , "A drop of optical moisture" , "Optical sign of sorrow" , "Droplet; rip" .)