Common tuber (6)
I believe the answer is:
potato
'common tuber' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for potato that I've seen before include "Plant tuber eaten as a vegetable" , "Maris Piper?" , "Vegetable with eyes" , "Edible tuber; hole in stocking (colloq.)" , "Food item (with eyes?)" .)