Law, say, revised constantly (6)
I believe the answer is:
always
'constantly' is the definition.
(I've seen this before)
'law say revised' is the wordplay.
'revised' indicates anagramming the letters.
'law'+'say'='lawsay'
'lawsay' with letters rearranged gives 'ALWAYS'.
(Other definitions for always that I've seen before include "Perpetually" , "Forever, on every occasion" , "Eternally" , "Invariably" , "Evermore" .)