Like a singular channel of reproduction (4)

I believe the answer is:

mono

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'like' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I can't see?

I don't understand how the rest of the clue works.

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(Other definitions for mono that I've seen before include "Single-speaker sound" , "Single-channel sound" , "Not stereo" , "Transmitting over one channel" .)

I've seen this clue in the Evening Standard.

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