Singer breaking rules (6)
I believe the answer is:
'rules' is the definition.
(reign can mean to rule or govern)
'singer breaking' is the wordplay.
'breaking' indicates anagramming the letters.
'singer' anagrammed gives 'REIGNS'.
(Other definitions for reigns that I've seen before include "Rules over like singer" , "Obtains" , "Rules over, occupies throne" , "Lords it over singer" , "Holds sway" .)