Star bit off vegetable (6)
I believe the answer is:
celery
'vegetable' is the definition.
(I know that celery is a type of vegetable)
I can't explain the rest of the clue.
(Other definitions for celery that I've seen before include "Vegetable with crisp stalks" , "The crunch matter for slimmer" , "Leafstalks eaten as a vegetable" , "Stick vegetable" , "Watery green vegetable" .)