Bird's periodical food (6)
I believe the answer is:
magpie
'bird's' is the definition.
(magpie is a kind of bird)
'periodical food' is the wordplay.
'periodical' becomes 'mag' (abbreviation for magazine).
'food' becomes 'pie' (pie is a kind of food).
'mag'+'pie'='MAGPIE'
(Other definitions for magpie that I've seen before include "Part of target" , "One on target" , "said to bring sorrow" , "Black-and-white crow" , "A black-and-white thieving bird" .)