Classic pie crust ingredient (4)
I believe the answer is:
lard
'classic pie crust ingredient' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lard that I've seen before include "Soft white semisolid fat" , "stuff with bacon" , "Hard cooking fat" , "White cooking fat" , "Pig fat used in cooking" .)