Deli jarful (4)
I believe the answer is:
mayo
'deli jarful' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for mayo that I've seen before include "You'll find it in the Emerald Isle" , "part of Ireland" , "Ir. county; salad dressing" , "Salad dressing (informal)" , "Cold, creamy sauce (abbr)" .)