Crazy slanderous remarks about celebrity in plant (4,7)
I believe the answer is:
wild mustard
'plant' is the definition.
(wild mustard is a kind of plant)
'crazy slanderous remarks about celebrity' is the wordplay.
'crazy' becomes 'wild' (I've seen this in other clues).
'slanderous remarks' becomes 'mud' (as in mud-slinging).
'about' means one lot of letters goes inside another.
'celebrity' becomes 'star' (I've seen this before).
'mud' enclosing 'star' is 'mustard'.
'wild'+'mustard'='WILD MUSTARD'
'in' acts as a link.
(Another definition for wild mustard that I've seen is " weed".)