Classical maid who always had the last word (4)

I believe the answer is:

echo

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'word' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for echo that I've seen before include "Comms code word for E" , "Marked by heat" , "Reflect in Czechoslovakia" , "repetitive" , "Noise heard again" .)

I've seen this clue in The Globe and Mail.

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