Poor harmony is leading issue in disco music (10)
I believe the answer is:
dissonance
'poor harmony' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'is leading issue in disco music' is the wordplay.
'leading' is a charade indicator (letters next to each other).
'issue' becomes 'son' (issue can mean someone's offspring).
'in' is an insertion indicator.
'disco music' becomes 'dance' (I can't justify this - if you can you should give a lot more credence to this answer).
'is'+'son'='isson'
'isson' going inside 'dance' is 'DISSONANCE'.
Can you help me to learn more?
(Other definitions for dissonance that I've seen before include "sounds harsh" , "Discordance" , "quartet?" , "Lack of harmony" , "Harsh sound" .)