Nasty hotel, so am moving (9)
I believe the answer is:
loathsome
'nasty' is the definition.
(thesaurus)
'hotel so am moving' is the wordplay.
'moving' indicates an anagram.
'hotel'+'so'+'am'='hotelsoam'
'hotelsoam' is an anagram of 'LOATHSOME'.
(Other definitions for loathsome that I've seen before include "Disgusting, nauseating" , "gross" , "Horrid" , "Hateful" , "15 [ABHORRENT]" .)