Taste of umami: soup flavouring in Japan (4)
I believe the answer is:
miso
'flavouring in japan' is the definition.
(flavouring in Japanese cuisine)
'taste of umami soup' is the wordplay.
'taste of' indicates the answer is hidden within the clue.
'MISO' can be found hidden inside 'umami soup'.
(Other definitions for miso that I've seen before include "Soya-beam paste" , "Thick paste used in Japanese soups and sauces" , "Soya bean paste" .)