....since he has become a citizen of Beijing (7)
I believe the answer is:
chinese
'citizen of beijing' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'since he has become a' is the wordplay.
'since he' anagrams to 'CHINESE'.
But, I'm unsure how this is indicated.
Can you help me to learn more?
(Other definitions for chinese that I've seen before include "in Eastern country" , "- Chequers; - leaves; - puzzle" , "Oriental language" , "Mandarin possibly" , "Language spoken by many" .)