Chinese region flier's to stay within (5)
I believe the answer is:
tibet
'chinese region' is the definition.
(I've seen this before)
'flier's to stay within' is the wordplay.
'flier' becomes 'tit' (type of bird).
'to stay' becomes 'be' (stay can mean to continue to be a certain way).
'within' means one lot of letters goes inside another.
'tit' going around 'be' is 'TIBET'.
(Other definitions for tibet that I've seen before include "woollen fabric" , "hilly region" , "Dalai Lama's orig. home" , "High mountainous area" , "State" .)