Grand Polish food (4)
I believe the answer is:
grub
'food' is the definition.
(grub is a kind of food)
'grand polish' is the wordplay.
'grand' becomes 'g' ('G' can be a synonym of 'grand').
'polish' becomes 'rub' (polish meaning rub to make shiny).
'g'+'rub'='GRUB'
(Other definitions for grub that I've seen before include "Caterpillar - food" , "Dig (up); hack writers' Street" , "food, commonly" , "Eats - larva" , "Food (informal)" .)