A spell in prison for a common girl (4)

I believe the answer is:

bird

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'girl' is the definition.
(I know that bird is a type of girl)

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

(Other definitions for bird that I've seen before include "Creature - time in prison" , "Prison time (slang)" , "Flier - spell in prison" , "Nest builder?" , "Booby, for example" .)

I've seen this clue in The Irish Independent.

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