Reflective navigation aid (5)
I believe the answer is:
radar
This clue could be a double definition.
'reflective navigation' is the first definition.
'radar' can be an answer for 'navigation' (thesaurus). I'm not sure about the 'reflective' bit.
'aid' is the second definition.
(I have seen 'Navigational aid ' mean 'radar' so perhaps 'aid' could also mean 'radar')
Can you help me to learn more?
(Other definitions for radar that I've seen before include "Method of detection" , "Ranging system" , "Means of detecting and locating distant objects" , "Kind of gun" , "Pulsed location-finder" .)