Solitude's difficult for the licentious (9)
I believe the answer is:
dissolute
'the licentious' is the definition.
(thesaurus)
'solitude's difficult' is the wordplay.
'difficult' is an anagram indicator.
'solitudes' is an anagram of 'DISSOLUTE'.
'for' is the link.
(Other definitions for dissolute that I've seen before include "O, lust dies when one is this loose in morals" , "Old tissue (anag) - like a rake?" , "Sensually overindugent" , "Duelist so (anag) - debauched" , "Sensually overindulgent" .)