Referring to bones, plan is faulty (6)
I believe the answer is:
spinal
'referring to bones' is the definition.
(the spine is made up of bones)
'plan is faulty' is the wordplay.
'faulty' indicates an anagram.
'plan'+'is'='planis'
'planis' anagrammed gives 'SPINAL'.
(Other definitions for spinal that I've seen before include "Of the vertebrae" , "of a vital column" , "Plains (anag.)" , "Member of dock family with edible stems" , "Type of column" .)