To finish, I have a salad plant (6)
I believe the answer is:
Here is my best explanation:
'a salad plant' is the definition.
(I've seen this before)
'to finish i have' is the subsidiary indication.
'to finish' becomes 'end' ('end' can be a synonym of 'finish').
'i have' becomes 'ive'.
(Other definitions for endive that I've seen before include "Vegetable", "Veined (anag) - salad plant", "Chicory", "Part of salad", "Portion of salad", "Edible plant", "salad ingredient", "Plant used in salads", "Envied the salad green badly" and "Salad plant related to chicory".)