Embarrassing adult rapping (8)
I believe the answer is:
abashing
'embarrassing' is the definition.
('abash' can be a synonym of 'embarrass')
'adult rapping' is the wordplay.
'adult' becomes 'a' (abbreviation).
'rapping' becomes 'bashing' (rap can mean to hit or bash).
'a'+'bashing'='ABASHING'
(Other definitions for abashing that I've seen before include "Causing to feel self-conscious" , "disconcerting" , "embarrassing" , "humiliating" .)