Dull, flavourless (7)
I believe the answer is:
insipid
This clue is a double definition.
'dull' is the first definition.
(similar in meaning)
'flavourless' is the second definition.
(synonyms)
(Other definitions for insipid that I've seen before include "Boring and lacking liveliness" , "Colourless" , "Wishy-washy" , "Very weak" , "without taste" .)