Lack of harmony (7)
'lack of harmony' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for discord that I've seen before include "Opposition" , "Dissension" , "cacophony" , "Strife, lack of harmony" , "contention" .)
(Other definitions for disunity that I've seen before include "conflict" , "Lack of solidarity" , "Lack of agreement" , "Lack of oneness" .)