Desirable person's improper message about urine container (6)
I believe the answer is:
sexpot
'desirable person's' is the definition.
(term for an attractive person)
'improper message about urine container' is the wordplay.
'improper message' becomes 'sext' (I have seen 'Explicit message' mean 'sext' so perhaps 'message' could also mean 'sext'. I am not sure about the 'improper' bit.).
'about' indicates putting letters inside.
'urine container' becomes 'po' (informal term for a chamber pot).
'sext' enclosing 'po' is 'SEXPOT'.
Can you help me to learn more?
(Other definitions for sexpot that I've seen before include "Attractive man" , "eg Craig? Lopez?" , "Babe" , "Hot bit of stuff" , "Tempting dish" .)