Remaining rule said to be reviewed (8)
I believe the answer is:
residual
'remaining' is the definition.
(I know that remaining can be written as residual)
'rule said to be reviewed' is the wordplay.
'to be reviewed' indicates anagramming the letters (letters reviewed or revised).
'rule'+'said'='rulesaid'
'rulesaid' with letters rearranged gives 'RESIDUAL'.
(Other definitions for residual that I've seen before include "Concerning what is left over" , "surplus" , "'Remaining, left over (8)'" , "Left over as a remainder" , "Leftover; repeat royalty" .)