Crossword Genius

Underwater detection system (5)

Ross

I believe the answer is:

sonar

'underwater detection system' is the definition.
(I've seen this before)

This is all the clue.

(Other definitions for sonar that I've seen before include "Locating device" , "location device" , "Undersea sensing system" , "System for locating underwater objects" , "Echo-location system" .)

I've seen this clue in the USA Today, the Evening Standard and the Sydney Morning Herald.
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