Mean to change a flower (7)
I believe the answer is:
anemone
'flower' is the definition.
(I know that anemone is a type of flower)
'mean to change a' is the wordplay.
'to change' indicates anagramming the letters.
'a' becomes 'one'.
'mean' with letters rearranged gives 'anem'.
'anem'+'one'='ANEMONE'
(Other definitions for anemone that I've seen before include "climbing plant" , "Kind of buttercup with white or coloured flowers" , "Plant; marine creature" , "Plant with bright flowers" , "bloomer" .)