Inoffensive article written in association with expert (15)

I believe the answer is:

unobjectionable

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'inoffensive' is the definition.
(similar in meaning)

'article written in association with expert' is the wordplay.
'article' becomes 'object' (both can mean a thing or item).
'written in' indicates putting letters inside.
'association with' becomes 'union' (I can't explain this - if you can you should give a lot more credence to this answer).
'expert' becomes 'able' (I've seen this in other clues).
'object' inserted inside 'union' is 'unobjection'.
'unobjection'+'able'='UNOBJECTIONABLE'

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I've seen this clue in The Daily Express.

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