Seaweed's flavour (4)
I believe the answer is:
tang
I believe this is a double definition.
'seaweed's' is the first definition.
(tang is a kind of seaweed)
'flavour' is the second definition.
('tang' can be a synonym of 'flavour')
(Other definitions for tang that I've seen before include "Piquancy - Chinese dynasty" , "Strong flavour" , "Strong taste or smell" , "Gnat (anag.)" , "Tart taste and Chinese dynasty" .)