Thin fog (4)
I believe the answer is:
mist
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">thin fog</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 mist that I've seen before include "Watery film" , "low-level cloud" , "Fret" , "Slight fog" , "Mizzle; light rain" .)