Promotes eradicating source of Government benefit (4)
I believe the answer is:
plus
'benefit' is the definition.
(thesaurus)
'promotes eradicating source of government' is the wordplay.
I cannot really understand how this works, but
'government' could be 'us' (U.S. is an example) and 'us' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for plus that I've seen before include "Advantage; also" , "Furthermore" , "credit" , "Something more" , "Add" .)