Nemesis, England invading state (7)
I believe the answer is:
avenger
'nemesis' is the definition.
(I've seen this before)
'england invading state' is the wordplay.
'england' becomes 'eng'.
'invading' indicates putting letters inside.
'state' becomes 'aver' (I've seen this before).
'eng' placed into 'aver' is 'AVENGER'.
(Other definitions for avenger that I've seen before include "One wanting retribution" , "He seeks satisfaction or retribution" , "Someone wanting to get even" , "One who retaliates -- engrave (anag)" , "Hillman" .)