One piece of biscuit per bird! (4)

I believe the answer is:

ibis

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'bird' is the definition.
(ibis is a kind of bird)

'one piece of biscuit per' is the wordplay.
'one' becomes 'I' (Roman numeral).
'piece of' indicates taking the first letters.
'per' becomes 'is' (I am not sure about this - if you are sure you should believe this answer much more).
The initial letter of 'biscuit' is 'b'.
'i'+'b'+'is'='IBIS'

Can you help me to learn more?

(Other definitions for ibis that I've seen before include "Winger" , "Eastern" , "Hotel group" , "seaside feeder?" , "Wading bird with a down-curved bill" .)

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