Picnic cabbage dish (8)
I believe the answer is:
coleslaw
(Other definitions for coleslaw that I've seen before include "Finely shredded raw cabbage with carrots and dressing as salad" , "Dish of shredded cabbage and carrot" , "accompaniment to Salad Days?" , "We locals consume shredded cabbage and carrots with dressing" , "Salad of mainly cabbage" .)