Rubbish government consumed by nastiness (5)
I believe the answer is:
bilge
'rubbish' is the definition.
(thesaurus)
'government consumed by nastiness' is the wordplay.
'government' becomes 'g'.
'consumed by' is an insertion indicator.
'nastiness' becomes 'bile'.
'g' put within 'bile' is 'BILGE'.
(Other definitions for bilge that I've seen before include "Rubbish, nonsense; dirty water in ship" , "Hogwash" , "Filthy water that collects in the bottom of a boat" , "Rubbish - water in boat" , "bull" .)