Supporter of NI remaining part of the UK
I believe the answer is:
unionist
'supporter of ni remaining part of the uk' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for unionist that I've seen before include "One doesn't want to break with Britain" , "Civil warmonger" , "TU member" , "Person supporting the political links between Great Britain and Northern Ireland" , "member of workers' association" .)