Leader ousted from one-time car plant (5)
I believe the answer is:
orris
'plant' is the definition.
The answer is an example.
'leader ousted from one-time car' is the wordplay.
'leader ousted from' means to remove the first letter.
'one-time car' becomes 'Morris' (Morris Minor, old make of car).
'morris' with its first letter taken away is 'ORRIS'.
(Other definitions for orris that I've seen before include "Preparation" , "perfumery ingredient" , "Fragrant rootstock" , "Perfume root" , "Iris root in perfumery" .)