One in, one out amongst anarchist's assembled followers (10)
I believe the answer is:
christians
'assembled followers' is the definition.
The answer and definition can be both people as well as being plural nouns.
Perhaps they are linked in a way I don't understand?
'one in one out amongst anarchist's' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'an' (an apple is one apple) and 'an' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for christians that I've seen is " Colosseum unfortunates".)