Pertaining to a foot bone (6)
I believe the answer is:
tarsal
'pertaining to a foot bone' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tarsal that I've seen before include "Foot bone" , "To do with bones of upper foot" , "One of the seven ankle bones" , "Of the bones making up the foot" .)