Innocent prince endlessly entertaining queen on ship (8)
I believe the answer is:
harmless
'innocent' is the definition.
(similar in meaning)
'prince endlessly entertaining queen on ship' is the wordplay.
I cannot really see how this works, but
'queen' could be 'r' (abbreviation for regina, e.g. in ER ) and 'r' is found in the answer.
'ship' could be 'ss' (prefix in ship names eg SS Great Britain) and 'ss' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for harmless that I've seen before include "Safe; innocent" , "Not producing any toxic effects" , "Causing no damage" , "Completely safe" , "Not injurious" .)