A vegetable Eric and Alec cooked (8)
I believe the answer is:
celeriac
'a vegetable' is the definition.
(celeriac is a kind of vegetable)
'eric and alec cooked' is the wordplay.
'and' says to put letters next to each other.
'cooked' indicates an anagram (letters cooked into a new form).
'eric' put after 'alec' is 'aleceric'.
'aleceric' is an anagram of 'CELERIAC'.
(Other definitions for celeriac that I've seen before include "Odd root vegetable for Alec Rice" , "It has a root like a turnip" , "Plant with a turnip-like 1 down" , "Edible root of a variety of celery plant" , "Turnip-rooted celery" .)