Moral significance (5)
I believe the answer is:
ethos
'moral significance' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ethos that I've seen before include "Spirit (of an age/culture)" , "Characteristic standards of those" , "Culture, way of life" , "Distinctive spirit of an institution" , "Character of a community or age" .)