Navigational instrument (7)
'navigational instrument' is the definition.
(compass is a kind of navigational instrument)
This is all the clue.
(Other definitions for compass that I've seen before include "Range, area" , "Navigational aid" , "Orienteering instrument" , "Navigational instrument" , "Box the ---, change fully round" .)
'navigational instrument' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sextant that I've seen before include "Mariner's instrument" , "Sighting instrument" , "Navigational aid" , "Navigator's instrument" , "Astronavigation instrument" .)