Fundamental values (5)
I believe the answer is:
ethos
'fundamental values' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ethos that I've seen before include "Distinctive spirit - character" , "Distinctive spirit of an institution" , "Moral character" , "Characteristic culture of a culture or time" , "Distinctive group spirit" .)