Meteorologist's device (9)
I believe the answer is:
barometer
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">meteorologist's device</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 barometer that I've seen before include "Weatherglass" , "Air-pressure measurer" , "Weather forecaster" , "Atmospheric pressure measurer" , "One showing pressure" .)