Tend to an overgrown plant (5)
I believe the answer is:
repot
'tend to an overgrown plant' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for repot that I've seen before include "Transplant" , "plant in another location" , "place somewhere new to put down roots" , "transfer seedlings" , "Give room to expand" .)