I believe the answer is:
'radicchio relative' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for endive that I've seen before include "Chicory-type salad vegetable" , "Veined (anag) - salad plant" , "Salad plant related to chicory" , "Plant used in salads" , "Envied (anag.)" .)