Abuse support, turning back on nation (8)

I believe the answer is:

diatribe

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'abuse' is the definition.
(I've seen this before)

'support turning back on nation' is the wordplay.
'support' becomes 'aid' ('aid' can be a synonym of 'support').
'turning back' is a reversal indicator.
'on nation' becomes 'tribe' (I can't justify this - if you can you should believe this answer much more).
'aid' reversed gives 'dia'.
'dia'+'tribe'='DIATRIBE'

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(Other definitions for diatribe that I've seen before include "Abusive harangue" , "provoking verbal onslaught" , "A Prolonged harangue" , "Passionate words" , "critical speech" .)

I've seen this clue in The Telegraph.

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