Rubbish government head consumed by bitterness (5)
I believe the answer is:
bilge
'rubbish' is the definition.
(thesaurus)
'government head consumed by bitterness' is the wordplay.
'head' says to take the initial letters.
'consumed by' is an insertion indicator.
'bitterness' becomes 'bile' (I've seen this in other clues).
The first letter of 'government' is 'g'.
'g' going within 'bile' is 'BILGE'.
(Other definitions for bilge that I've seen before include "(Water at) bottom of ship" , "Dirty water in bottom of boat - drivel - nonsense" , "Piffle - part of hull" , "Hogwash" , "Nonsense (informal)" .)