Initial flavour in exotic Mirin is weak (6)
I believe the answer is:
infirm
'weak' is the definition.
(synonyms)
'initial flavour in exotic mirin' is the wordplay.
'initial' suggests taking the first letters.
'in' indicates putting letters inside.
'exotic' is an anagram indicator (an unusual form of the letters).
The initial letter of 'flavour' is 'f'.
'mirin' is an anagram of 'inirm'.
'f' inserted within 'inirm' is 'INFIRM'.
'is' is the link.
(Other definitions for infirm that I've seen before include "stable? No" , "Not in good health" , "Doddery" , "Physically weak as from old age" , "'Weak, ill (6)'" .)