One million people who tweet possibly could be bots? (9)
I believe the answer is:
imposters
'tweet possibly could be bots?' is the definition.
I can't judge whether this definition defines the answer.
'one million people' is the wordplay.
'one million' becomes 'im' (resembles pm).
'people' becomes 'posters' (I am not sure about this - if you are sure you should believe this answer much more).
'im'+'posters'='IMPOSTERS'
'who' is the link.
Can you help me to learn more?
(Other definitions for imposters that I've seen before include "Fakes" , "They assume identities in order to deceive" .)