Back in nurseries to order plants (5)
I believe the answer is:
roots
'plants' is the definition.
The answer is an example.
'back in nurseries to order' is the wordplay.
'back' shows that the letters should be reversed in order.
'in' says the answer is hidden in the clue.
'stoor' is hidden in the letters of 'nurseries to order'.
'stoor' back-to-front is 'ROOTS'.
(Other definitions for roots that I've seen before include "Genealogy" , "(Family) origins" , "one's ancestry" , "eg Parsnips" , "Origins, of plants or people" .)