Relative to resist change (6)
I believe the answer is:
sister
'relative' is the definition.
(I know that Sister is a type of sibling)
'resist change' is the wordplay.
'change' indicates anagramming the letters.
'resist' is an anagram of 'SISTER'.
'to' is the link.
(Other definitions for sister that I've seen before include "Resits (anag.)" , "Female relation" , "habits' - one who has them" , "Close relation" , "Nurse, nun and sibling" .)