Rue prince's ludicrous lasciviousness (9)
I believe the answer is:
prurience
'lasciviousness' is the definition.
(synonyms)
'rue prince's ludicrous' is the wordplay.
'ludicrous' indicates anagramming the letters.
'rue'+'prince'='rueprince'
'rueprince' anagrammed gives 'PRURIENCE'.
(Other definitions for prurience that I've seen before include "Unhealthy interest in sex" , "Unhealthy interest in sexual matters" , "Salaciousness" , "Lust" , "Lewdness -- epic rerun (anag)" .)