Flier born to get out of line? (5)

I believe the answer is:

robin

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'flier' is the definition.
(robin is a kind of birdanimal)

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

(Other definitions for robin that I've seen before include "Bird - boy's name" , "Small brown and red bird" , "Bird; Batman's aide" , "Small songbird" , "Christmas songbird" .)

I've seen this clue in the Evening Standard.

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