Shabby corporation milked old opponents (10)

I believe the answer is:

tumbledown

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'shabby' is the definition.
(thesaurus)

'corporation milked old opponents' is the wordplay.
'corporation' becomes 'tum' (I've seen this before).
'milked' becomes 'bled' (I've seen this in another clue).
'old opponents' becomes 'own' (I can't explain this - if you can you should give a lot more credence to this answer).
'tum'+'bled'+'own'='TUMBLEDOWN'

Can you help me to learn more?

(Other definitions for tumbledown that I've seen before include "threatening to fall" , "collapsed" , "Ramshackle" , "Derelict" , "in a dilapidated state" .)

I've seen this clue in The Independent.

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