Forenames rearranged, one's in order (9)
I believe the answer is:
freemason
'one's in order' is the definition.
(order meaning a particular society or group)
'forenames rearranged' is the wordplay.
'rearranged' is an anagram indicator.
'forenames' anagrammed gives 'FREEMASON'.
(Other definitions for freemason that I've seen before include "Forenames of one of fraternity with secret rituals" , "Brother" , "secret society member" , "His order's a secret one" , "One on the square" .)