Consequence of reforming Ulster (6)
I believe the answer is:
result
'consequence' is the definition.
(I know that consequence can be written as result)
'reforming ulster' is the wordplay.
'reforming' indicates anagramming the letters.
'ulster' with letters rearranged gives 'RESULT'.
'of' is the link.
(Other definitions for result that I've seen before include "Rustle (anag.)" , "Final score" , "Consequence in Ulster (6)" , "Verdict" , "'Outcome, consequence (6)'" .)