Cuban piece of cake with no duplicated ingredients? (5)

I believe the answer is:

rumba

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'cuban piece' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe there's a link between them I don't understand?

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(Other definitions for rumba that I've seen before include "Style of dance" , "Burma (anag)" , "Cuban folk-dance" , "Cuban folk dance" , "music one can dance to" .)

I've seen this clue in The Guardian.

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