Crossword Genius

Boast to a flyer (4)

Ross

I believe the answer is:

crow

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'boast' is the definition.
(to crow about something is to boast about it)

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for crow that I've seen before include "Brave" , "Black bird with raucous call" , "Native American -- bird" , "Express gleeful triumph" , "Common bird" .)

I've seen this clue in The Mirror.
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