Chocolate bar to snap (5)

I believe the answer is:

topic

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'chocolate bar' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps there's an association between them I don't understand?

'to snap' is the wordplay.
'snap' becomes 'pic' (short for picture).
'to'+'pic'='TOPIC'

Can you help me to learn more?

(Other definitions for topic that I've seen before include "That may be debatable" , "Subject (of, eg, speech)" , "Subject (of speech, etc)" , "Something to discuss" , "A subject for conversation or debate" .)

I've seen this clue in The Independent.

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