Navigation aid that looks both ways (5)

I believe the answer is:

radar

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This could be a double definition.

'navigation aid that looks' is the first definition.
'radar' can be an answer for 'navigation' (thesaurus). I am not certain of the remainder of the definition.

'both ways' is the second definition.

Can you help me to learn more?

(Other definitions for radar that I've seen before include "Gluttony" , "Ranging system" , "What shows range" , "Radio detection system" , "System for detecting things using radio waves" .)

I've seen this clue in The Daily Express and The Mirror.

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