Motley beast or bad boy once (8)
I believe the answer is:
Here is my best explanation:
'motley' is the definition.
('assorted' can be a synonym of 'motley')
'beast or bad boy once' is the subsidiary indication.
'beast' becomes 'ass' (I've seen this before).
'bad boy once' becomes 'ted' (reference to 1950s subculture Teddy Boys).
(Other definitions for assorted that I've seen before include "Miscellaneous, sundry", "Classified", "Various, diverse", "Of different kinds put together, like sweets", "Motley", "Of different kinds put together, say sweets", "Of various types put together", "Sundry", "Of various kinds" and "Stared so at a varied mixture as of sweets".)