Author is questioned about adult (6)
I believe the answer is:
risque
'adult' is the definition.
(I know that adult can be written as risque)
'author is questioned about' is the wordplay.
'about' indicates the answer is hidden within the clue (the clue goes around or about the answer).
'RISQUE' is hidden in the letters of 'author is questioned'.
(Other definitions for risque that I've seen before include "Bawdy" , "Suggestive - naughty" , "Slightly indecent or racy" , "Slightly improper" , "Daring" .)