Conservative? Barnet is moderate (5)
I believe the answer is:
chair
'moderate' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for chair that I've seen before include "Windsor, for example" , "Preside, guide meeting" , "Supporter" , "Prof's post; meeting leader" , "Seat (of learning?)" .)