Crossword Genius

Old charitable company waived for taxing (7)

Ross

I believe the answer is:

onerous

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'taxing' is the definition.
(synonyms)

I don't understand how the remainder of the clue works.

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(Other definitions for onerous that I've seen before include "Burdensome, heavy kind of duty" , "quite a burden if so" , "'Heavy, burdensome (7)'" , "Challenging" , "weight" .)

I've seen this clue in The Hindu.
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