Backbone in apparition? (6)
I believe the answer is:
spirit
This clue is a double definition.
'backbone' is the first definition.
(thesaurus)
'apparition?' is the second definition.
(apparition is a kind of spirit)
'in' acts as a link.
(Other definitions for spirit that I've seen before include "Animating force within living things" , "bottle?" , "Vivacity" , "25 28 [MARS LANDER]" , "enthusiasm" .)