Weed in extremely demure clothing along with hero (9)
I believe the answer is:
dandelion
'weed' is the definition.
(plant classified as a weed)
'extremely demure clothing along with hero' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'clothing' is an insertion indicator (some letters cover up or clothe others).
'along with' becomes 'and' (I've seen this in another clue).
'hero' becomes 'lion' (lion can mean a brave person).
'demure' with its centre taken out is 'de'.
'de' going around 'and' is 'dande'.
'dande'+'lion'='DANDELION'
'in' acts as a link.
(Other definitions for dandelion that I've seen before include "It has a bright yellow flower followed by a fluffy seed ball" , "Common yellow-flowered plant" , "Flower with a "clock"" , "salad plant" , "I nod, laden with yellow flower" .)