Navigation instrument (7)
I believe the answer is:
sextant
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">navigation instrument</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 sextant that I've seen before include "I'll tell you where sailors are" , "Measuring instrument on board" , "Nautical instrument for measuring angular distances" , "Astronavigation instrument" , "Sighting instrument" .)