Thai cuisine herb (5)
I believe the answer is:
basil
'thai cuisine herb' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for basil that I've seen before include "A herb; Cardinal --- Hume" , "Aromatic herb in pesto" , "Culinary plant" , "Fragrant herb" , "Sweet-smelling herb" .)