Centre of revolution (3)
I believe the answer is:
hub
This clue could be a double definition.
'centre' is the first definition.
(hub is a kind of centre)
'revolution' is the second definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for hub that I've seen before include "throbbing heart" , "Centre or axis" , "Focal point of activity" , "Focus" , "Centre of activity" .)