Sequel to Ulster novel (6)
I believe the answer is:
result
'sequel' is the definition.
(thesaurus)
'ulster novel' is the wordplay.
'novel' indicates an anagram.
'ulster' with letters rearranged gives 'RESULT'.
'to' is the link.
(Other definitions for result that I've seen before include "Rustle (anag.)" , "Consequence in Ulster (6)" , "Effect - outcome" , "Outcome of an undertaking" , "Effect of lustre" .)