Instigated raunchy frolic in private with Duke (8)
I believe the answer is:
prompted
'instigated' is the definition.
('prompt' can be a synonym of 'instigate')
'raunchy frolic in private with duke' is the wordplay.
'raunchy frolic' becomes 'romp' (synonyms. I am not sure about the 'raunchy' bit.).
'in' is an insertion indicator.
'private' becomes 'pte'.
'with' is a charade indicator (letters next to each other).
'duke' becomes 'd' (abbreviation).
'romp' put within 'pte' is 'prompte'.
'prompte'+'d'='PROMPTED'
Can you help me to learn more?
(Other definitions for prompted that I've seen before include "Given help with speech" , "Instigated" .)