Oneness (5)
'oneness' is the definition.
(synonyms)
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" .)