Govern party with comrade keeping popular (8)
I believe the answer is:
dominate
'govern' is the definition.
(I've seen this before)
'party with comrade keeping popular' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'with' means one lot of letters go next to another.
'comrade' becomes 'mate' (I've seen this in other clues).
'keeping' is an insertion indicator.
'popular' becomes 'in'.
'mate' enclosing 'in' is 'minate'.
'do'+'minate'='DOMINATE'
(Other definitions for dominate that I've seen before include "Rule" , "Admit one in order to be in control" , "Be lord over" , "Command, control" , "Tower over" .)