Crossword Genius

Echo-sounding device (5)

Ross

I believe the answer is:

asdic

(Other definitions for asdic that I've seen before include "old detection method" , "Early form of sonar" , "Early echo-sounder; a disc (anag.)" , "Submarine detection device" , "It once sounded" .)

I've seen this clue in the Sydney Morning Herald.
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