Charlie stirred paint in plant (6)
I believe the answer is:
catnip
'plant' is the definition.
(catnip is a kind of plant)
'charlie stirred paint in' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'stirred' is an anagram indicator.
'in' means one lot of letters goes inside another.
'paint' is an anagram of 'atnip'.
'c' put inside 'atnip' is 'CATNIP'.
(Other definitions for catnip that I've seen before include "Kitty likes that!" , "Strong-smelling herb" , "Plant with scented leaves which felines like" , "feline favourite?" , "Herb of the mint family, attractive to some pets" .)