Rule check discussed (5)
I believe the answer is:
reign
'rule' is the definition.
(I know that reign is a type of rule)
'check discussed' is the wordplay.
'check' becomes 'rein' (both can mean to control or limit).
'discussed' shows a homophone (sound like).
'rein' is a homophone of 'REIGN'.
(Other definitions for reign that I've seen before include "time in power" , "Period of monarch" , "Dominion" , "Period of the rule of a sovereign" , "Sovereignty" .)