In a riot, ensnared, let go of ringleader of groups of nine (7)
I believe the answer is:
enneads
'groups of nine' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for enneads that I've seen before include "Sane end (anag.)" , "groups of nine" , "Groups appearing one over the eight" , "Eights plus coxes, perhaps" , "Groups with members one over the eight" .)