Answer:

CORE

Answer	Crossword Clue
CORE	Apple throwaway
CORE	Computer memory, in the old days
CORE	Heart of the matter

CORE	Pear throwaway
CORE	Prepare apples
CORE	Reactor part
CORE	Apple leftover
CORE	Innermost part
CORE	Part of the earth
CORE	Sum and substance
CORE	Apple remnant

CORE	Heart of a nuclear reactor
CORE	Apple center
CORE	Apple refuse
CORE	For all, in curricula
CORE	Granny Smith's heart
CORE	Heart
CORE	Center of the earth
CORE	Baldwin discard

CORE	Crunch target
CORE	Pith
CORE	Geological sample
CORE	Central part
CORE	Fundamental
CORE	Innermost
CORE	Apple discard
CORE	Central section

CORE	Fruit center
CORE	Kind of curriculum
CORE	Planetary center
CORE	Center
CORE	Pear discard
CORE	Apple part
CORE	Apple heart
CORE	Rome Beauty's heart

CORE	Delicious discard
CORE	Kind of requirements for a college student
CORE	Apple seeds' site
CORE	Essence
CORE	The part of an apple most folks don't eat