Start to draw lots for casual artwork (7)
I believe the answer is:
doodles
'casual artwork' is the definition.
'start to draw lots' is the wordplay.
'start to' suggests taking the first letters.
'lots' becomes 'oodles' (synonyms).
The first letter of 'draw' is 'd'.
'd'+'oodles'='DOODLES'
'for' acts as a link.
(Other definitions for doodles that I've seen before include "Scribbles absent-mindedly" , "makes drawings absentmindedly" , "Scribbled drawings" , "Aimless drawings" , "Idle drawings" .)