Say law needs changing continually (6)
I believe the answer is:
always
'continually' is the definition.
(thesaurus)
'say law needs changing' is the wordplay.
'needs changing' indicates an anagram (I've seen this in other clues).
'say'+'law'='saylaw'
'saylaw' is an anagram of 'ALWAYS'.
(Other definitions for always that I've seen before include "Constantly" , "whatever the circumstances" , "Continually" , "Perpetually" , "Forevermore" .)