Took on work in Bill & Ted (7)
I believe the answer is:
adopted
'took on' is the definition.
('adopt' can be a synonym of 'take on')
'work in bill ted' is the wordplay.
'work' becomes 'op' (common abbreviation for 'opus').
'in' is an insertion indicator.
'bill' becomes 'ad' (advertisement stuck on wall).
'ad'+'ted'='adted'
'op' going within 'adted' is 'ADOPTED'.
(Other definitions for adopted that I've seen before include "Took into one's family" , "Fostered - assumed" , "Chose to follow" , "Taken as one's own" , "Took under one's wing" .)