Be in bird country (5)
I believe the answer is:
tibet
'country' is the definition.
(Tibet is an example)
'be in bird' is the wordplay.
'in' indicates putting letters inside.
'bird' becomes 'tit' (tit is a kind of bird).
'be' put inside 'tit' is 'TIBET'.
(Other definitions for tibet that I've seen before include "region out East" , "Dalai Lama's orig. home" , "Part of Asia" , "Nominally autonomous region of China" , "woollen fabric" .)