Answer: backbone

AnswerCrossword Clue
BACKBONEFortitude
BACKBONESpine
BACKBONEResolve
BACKBONEWimp's lack
backbonethe spine (the vertebral column)
backboneStrength of character; firmness
backboneThe main chain of a polymeric molecule
backboneThe spine of a book
backboneThe chief support of a system or organization; the mainstay
backboneA high-speed, high-capacity digital connection which forms the axis of a local or wide area network