Sharp as tacks that conceal food (5)
I believe the answer is:
pasta
'food' is the definition.
(pasta is a kind of food)
'sharp as tacks that conceal' is the wordplay.
'that conceal' says the answer is hidden in the clue.
'PASTA' is hidden in the letters of 'sharp as tacks'.
(Other definitions for pasta that I've seen before include "Shaped and dried dough" , "Dried flour paste used in cooking Italian dishes" , "Staple Italian food base" , "Dish of dough made with durum wheat" , "The stuff of spaghetti, macaroni etc" .)