Plant some now as a biennial (6)
I believe the answer is:
wasabi
'plant' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see an association between them that I can't see?
'some now as a biennial' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'WASABI' is hidden within 'now as a biennial'.
Can you help me to learn more?
(Other definitions for wasabi that I've seen before include "Hollyhock" , "Flavouring used in Japanese cuisine" , "Pungent green root, used in Japanese cooking" , "Pungent green root used in Japanese cookery" , "Pungent green paste used in Japanese cuisine" .)