Editor backed language rule (6)
I believe the answer is:
decree
'rule' is the definition.
(I know that rule can be written as decree)
'editor backed language' is the wordplay.
'editor' becomes 'ed' (abbreviation).
'backed' shows that the letters should be reversed in order.
'language' becomes 'cree' (Cree is an example).
'ed' written backwards gives 'de'.
'de'+'cree'='DECREE'
(Other definitions for decree that I've seen before include "An official proclamation or ruling" , "Judgment of a court" , "Legally-binding command or decision" , "Direct" , "Recede (anag.)" .)