From the City getting a call, call back (4)

I believe the answer is:

echo

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'call back' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for echo that I've seen before include "Bounced sound" , "Nymph (only able to repeat the last words of others)" , "one catches on the rebound?" , "Comms code word for E" , "Reproduction" .)

I've seen this clue in the Evening Standard.

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