Throw out scarf in show of gratitude (5,3)

I believe the answer is:

thank you

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But I can't explain it at all! Could you help me understand?

(Other definitions for thank you that I've seen before include "show appreciation" , "Ta" , "Concentional expression of appreciation" , "Much obliged!" , "Words of gratitude" .)

I've seen this clue in The Hindu.

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