Bird chewing a pencil (7)
I believe the answer is:
pelican
'bird' is the definition.
(pelican is a kind of bird)
'chewing a pencil' is the wordplay.
'chewing' is an anagram indicator.
'a'+'pencil'='apencil'
'apencil' is an anagram of 'PELICAN'.
(Other definitions for pelican that I've seen before include "In place for large-billed bird" , "Bird, large bag under bill" , "Does its beak hold more that its belly can?" , "Large-billed waterbird" , "Its beak holds more than its belly can" .)