Demolished hot meal, so becoming obnoxious (9)
I believe the answer is:
loathsome
'obnoxious' is the definition.
(thesaurus)
'demolished hot meal so' is the wordplay.
'demolished' indicates an anagram.
'hot'+'meal'+'so'='hotmealso'
'hotmealso' anagrammed gives 'LOATHSOME'.
'becoming' is the link.
(Other definitions for loathsome that I've seen before include "Disgusting, nauseating" , "Horrid" , "15 [ABHORRENT]" , "gross" , "Hateful" .)