Reigned soundly, albeit under restriction (6)
I believe the answer is:
reined
'albeit under restriction' is the definition.
I can't tell whether this defines the answer.
'reigned soundly' is the wordplay.
'soundly' shows a homophone (sound like).
'reigned' is a homophone of 'REINED'.
Can you help me to learn more?
(Other definitions for reined that I've seen before include "Stopped or slowed a horse" , "Restrained" , "Pulled in, checked progress" .)