Characteristic spirit of a culture or era (5)
I believe the answer is:
ethos
'characteristic spirit of a culture or era' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ethos that I've seen before include "Distinctive group spirit" , "Distinctive attitudes of a people" , "Characteristic culture of a culture or time" , "Philosophy" , "Spirit (of a group, say)" .)