Advance, say, bombed nation rued (5,5)

I believe the answer is:

trade union

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'advance' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'bombed nation rued' is the wordplay.
'bombed' indicates anagramming the letters.
'nation'+'rued'='nationrued'
'nationrued' anagrammed gives 'TRADE-UNION'.

'say' acts as a link.

Can you help me to learn more?

(Other definitions for trade union that I've seen before include "Equity perhaps" , "Organised Labour" , "Equity is one such" .)

I've seen this clue in The Telegraph.

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