Crossword Genius

I, for one, heard the affirmation (6)

Ross

I believe the answer is:

avowal

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'affirmation' is the definition.
(synonyms)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for avowal that I've seen before include "testimony?" , "Positive declaration" , "Profession of" , "Assertive declaration" , "Open assertion" .)

I've seen this clue in The Hindu.
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