Send a message from the heart of comradely unions (5)

I believe the answer is:

radio

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'send a message' is the definition.
(I've seen this before)

'heart of comradely unions' is the wordplay.
'heart of' indicates the central letters.
'unions' becomes 'io' (I am not sure about this - if you are sure you should believe this answer much more).
The middle of 'comradely' is 'rad'.
'rad'+'io'='RADIO'

'from the' acts as a link.

Can you help me to learn more?

(Other definitions for radio that I've seen before include "It used to be called the wireless" , "Speech receiver" , "send a message" , "means of communication" , "MW, LW or FM sound source" .)

I've seen this clue in The Irish Times.

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