Navigating aid looks both ways (5)
I believe the answer is:
radar
'both ways' is the definition.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for radar that I've seen before include "Navigation aid" , "Technique using beam" , "Measuring device that locates distant objects" , "Position detector using radio wave pulses" , "Locator of plane" .)