Flower for bully - mistake (7)
I believe the answer is:
cowslip
'flower' is the definition.
(I've seen this before)
'bully mistake' is the wordplay.
'bully' becomes 'cow' (cow can mean to bully or oppress).
'mistake' becomes 'slip' (a slip is a blunder or mistake).
'cow'+'slip'='COWSLIP'
'for' acts as a link.
(Other definitions for cowslip that I've seen before include "Flowering plant" , "Yellow spring flower" , "Plant with yellow flower" , "Wild spring flower" , "Pretty little wild flower for unsteady bovine" .)