Section including rook, duck, and another bird (6)
I believe the answer is:
parrot
'bird' is the definition.
(parrot is a kind of bird)
'section including rook duck' is the wordplay.
'section' becomes 'part' ('part' can be a synonym of 'section'**).
'including' is an insertion indicator.
'rook' becomes 'r' (abbreviation in chess).
'duck' becomes 'o'.
'r'+'o'='ro'
'part' enclosing 'ro' is 'PARROT'.
'and another' acts as a link.
(Other definitions for parrot that I've seen before include "Bird (that repeats)" , "Chant" , "Copycat who does not understand words or acts imitated" , "Mechanically repeat; bird" , "Mimic speech like colourful bird" .)