Chairman’s dreadful political doctrine (9)
I believe the answer is:
anarchism
'political doctrine' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'chairman's dreadful' is the wordplay.
'dreadful' indicates an anagram.
'chairmans' with letters rearranged gives 'ANARCHISM'.
Can you help me to learn more?
(Other definitions for anarchism that I've seen before include "lawless attitude" , "Man's chair (anag.)" , "Bakunin advocated it" , "anti-government doctrine" , "Anti-government ideology" .)