Northern Ireland border rejected Japanese wine (5)
I believe the answer is:
mirin
'japanese wine' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'northern ireland border rejected' is the wordplay.
'northern ireland' becomes 'NI' (abbreviation).
'border' becomes 'rim' (both can mean an edge).
'rejected' shows that the letters should be reversed in order.
'ni'+'rim'='nirim'
'nirim' backwards is 'MIRIN'.
Can you help me to learn more?
(Another definition for mirin that I've seen is " Rice wine used in Japanese cookery".)