To pot a new plant (6)
I believe the answer is:
potato
'plant' is the definition.
(potato is a kind of plant)
'to pot a new' is the wordplay.
'new' indicates anagramming the letters.
'to'+'pot'+'a'='topota'
'topota' is an anagram of 'POTATO'.
(Other definitions for potato that I've seen before include "Inert person" , "Maris Piper?" , "Spud (6)" , "Root crop" , "Murphy (informal)" .)