Good government has merely to disregard outsiders and follow party lines (8)
I believe the answer is:
doggerel
'lines' is the definition.
(lines of poor quality poetry)
'good government has merely to disregard outsiders and follow party' is the wordplay.
'good government' becomes 'gg' (this might be a standard abbreviation which I don't know about).
'has' says to put letters next to each other.
'to disregard outsiders' says to take the centre (letters on the outside are removed).
'and follow' is a charade indicator (letters next to each other).
'party' becomes 'do' (do is a kind of party).
The middle of 'merely' is 'erel'.
'gg' put next to 'erel' is 'ggerel'.
'ggerel' put after 'do' is 'DOGGEREL'.
(Other definitions for doggerel that I've seen before include "Unpretentious verses" , "Verse lacking artistry" , "trivial lines" , "Very bad poetry or verse" , "Nonsense verse" .)