A minor disagreement (5)
I believe the answer is:
This clue might be a double definition.
'a minor' is the first definition.
(thesaurus)
'disagreement' is the second definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
Can you help me to learn more?
(Other definitions for major that I've seen before include "Significant; rank" , "1 down's predecessor" , "Of great importance" , "grave" , "Of greater importance or stature" .)