Oneness (9)
'oneness' is the definition.
(I know that oneness can be written as unity)
This is the entire clue.
(Other definitions for unity that I've seen before include "State of being joined as a whole" , "Oneness, harmony" , "Number one" , "One - mutual agreement" , "Accord" .)
(Other definitions for unanimity that I've seen before include "Total accord" , "State of accord, no one dissenting" , "State of total agreement" , "Mutiny in a state of complete agreement" .)