Rules changed for a singer (6)

I believe the answer is:

reigns

I'm a little stuck... Click here to teach me more about this clue!

'rules' is the definition.
(reign can mean to rule or govern)

'changed for a singer' is the wordplay.
'singer' anagrams to 'REIGNS'.
However, I am unsure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for reigns that I've seen before include "Holds sway" , "Rules over like singer" , "Singer who governs" , "Rules as monarch" , "Rules over, occupies throne" .)

I've seen this clue in the Evening Standard.

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