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' indicates putting letters inside.
'private' becomes 'pte'.
'with' means one lot of letters go next to another.
'duke' becomes 'd' (abbreviation).
'romp' put into '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" .)