Daughter with European cat weed (9)
I believe the answer is:
dandelion
'weed' is the definition.
(plant classified as a weed)
'daughter with european cat' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'with' becomes 'and'.
'european' becomes 'E' (abbreviation e.g. EU).
'cat' becomes 'lion' (lion is a kind of cat).
'd'+'and'+'e'+'lion'='DANDELION'
(Other definitions for dandelion that I've seen before include "Common yellow-flowered weed" , "salad plant" , "Common yellow-flowered plant" , "salad leaves" , "Weed with deeply incised leaves" .)