Rules for a bad singer? (6)
I believe the answer is:
'rules' is the definition.
(I know this)
'bad singer?' is the wordplay.
'bad' indicates anagramming the letters.
'singer' is an anagram of 'REIGNS'.
'for a' acts as a link.
(Other definitions for reigns that I've seen before include "Periods of sovereign rule" , "Holds sway" , "Rules as monarch" , "Rules as sovereign" , "Rules over, occupies throne" .)