Root weeds out (5)
I believe the answer is:
swede
'root' is the definition.
(I know that swede is a type of root vegetable)
'weeds out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'weeds' anagrammed gives 'SWEDE'.
(Other definitions for swede that I've seen before include "Large root vegetable" , "Scandinavian - vegetable" , "Northern European" , "N European" , "Nobel for one" .)