Justice after English blokes upset relative (7)
I believe the answer is:
nemesis
'justice' is the definition.
(I have seen 'Vengeful justice ' mean 'nemesis' so perhaps 'justice' could also mean 'nemesis')
'english blokes upset relative' is the wordplay.
'english' becomes 'E' (abbreviation).
'blokes' becomes 'men' (bloke can informally mean a man).
'upset' says the letters should be written in reverse.
'relative' becomes 'sis' (short for sister).
'e'+'men'='emen'
'emen' written backwards gives 'neme'.
'neme'+'sis'='NEMESIS'
'after' is the link.
(Other definitions for nemesis that I've seen before include "Archenemy" , "Siemens (anag.)" , "Bane" , "Nee Miss (anag.)" , "Goddess of revenge - seems in (anag)" .)