Ideological suffix (3)
I believe the answer is:
ism
'ideological suffix' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ism that I've seen before include "Suffix denoting doctrine or practice" , "Unspecified doctrine" , "Any system of beliefs" , "Belief system" , "Informal doctrine found in Bismarck" .)