Banality (6)
I believe the answer is:
truism
'banality' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for truism that I've seen before include "Saying that's obviously accurate" , "Unoriginal and obviously correct statement" , "Obviously correct and verified statement" , "self-evident statement" , "An obvious statement that says noting new or interesting" .)