Wind speed measurer (10)
I believe the answer is:
anemometer
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wind speed measurer</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for anemometer that I've seen before include "Wind speed instrument" , "Wind speed measurer" , "Air Force display unit?" , "Wind speed gauge" , "Meaner to me (anag)" .)