Casually draws lots after onset of dispute (7)
I believe the answer is:
doodles
'casually draws' is the definition.
'doodles' can be an answer for 'draws' (doodling is a kind of drawing). I'm not sure about the 'casually' bit.
'lots after onset of dispute' is the wordplay.
'lots' becomes 'oodles' (informal term for a large amount).
'after' is a charade indicator (letters next to each other).
'onset of dispute' becomes 'd' (I can't explain this - if you can you should give a lot more credence to this answer).
'oodles' after 'd' is 'DOODLES'.
Can you help me to learn more?
(Other definitions for doodles that I've seen before include "Scribbled drawings" , "rough sketches" , "Scribbles absent-mindedly" , "makes drawings absentmindedly" , "Idle drawings" .)