...friends bringing in extremely unjust changes (7)
I believe the answer is:
mutates
'changes' is the definition.
(to mutate is to change or transform)
'friends bringing in extremely unjust' is the wordplay.
'friends' becomes 'mates' (mate is a kind of friend).
'bringing in' means one lot of letters goes inside another.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'unjust' with its centre taken out is 'ut'.
'mates' going around 'ut' is 'MUTATES'.
(Another definition for mutates that I've seen is " Changes into something else".)