Go by plant (6)
I believe the answer is:
pepper
'plant' is the definition.
The answer is an example.
'go by' is the wordplay.
'go' becomes 'pep' (I've seen this before).
'by' becomes 'per'.
'pep'+'per'='PEPPER'
(Other definitions for pepper that I've seen before include "Sprinkle - condiment" , "Pungent condiment" , "Riddle" , "Pelt" , "Dot" .)