Lecherousness (4)
I believe the answer is:
'lecherousness' is the definition.
(I know that lecherousness can be written as lust)
This is all the clue.
(Other definitions for lust that I've seen before include "Libido" , "Carnal desire" , "Passionate desire" , "Deadly sin of extreme passion" , "Intense sexual desire, a deadly sin" .)