Legal dispute was resolved by union: fired up about that (7)
I believe the answer is:
lawsuit
'legal dispute' is the definition.
(I've seen this before)
'was resolved by union fired up about that' is the wordplay.
'resolved' is an anagram indicator.
'by' means one lot of letters go next to another.
'union' becomes 'U' (common abbreviation as in Trades Union Congress).
'fired up' becomes 'lit' (I've seen this in another clue).
'about that' indicates putting letters inside.
'was' with letters rearranged gives 'aws'.
'aws'+'u'='awsu'
'awsu' put into 'lit' is 'LAWSUIT'.
(Other definitions for lawsuit that I've seen before include "Legal case" , "Dispute brought to court" , "The process of bringing action in legal court" , "Process of bringing dispute or claim before the courts" , "Claim brought to court" .)