A plant we name (4)
I believe the answer is:
weed
'a plant' is the definition.
(weed is a kind of plant)
'we name' is the wordplay.
'name' becomes 'ed' (short for edward).
'we'+'ed'='WEED'
(Other definitions for weed that I've seen before include "Hoe to remove it" , "nuisance in bed" , "Troublesome plant" , "Marijuana (slang)" , "Plant growing where it is not wanted" .)