Ne'er-do-well has to settle a fight (8)
I believe the answer is:
layabout
'ne'er-do-well' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's an association between them I don't understand?
'to settle a fight' is the wordplay.
'to settle' becomes 'lay' (I can't justify this - if you can you should believe this answer much more).
'fight' becomes 'bout' (as in a bout in boxing).
'lay'+'a'+'bout'='LAYABOUT'
'has' is the link.
Can you help me to learn more?
(Other definitions for layabout that I've seen before include "good-fornothing" , "lazy fellow" , "Idler" , "work-shy type" , "Lazybones" .)