Continually add anything different (5,3,3)
I believe the answer is:
night and day
'continually' is the definition.
(thesaurus)
'add anything different' is the wordplay.
'different' is an anagram indicator.
'add'+'anything'='addanything'
'addanything' anagrammed gives 'NIGHT AND DAY'.
(Other definitions for night and day that I've seen before include "24 - 7" , "Cole Porter music" , "Play" , "twenty-four hours in length?" , "All the time (Sinatra song)" .)