Support position of white knight in resolution (8)
I believe the answer is:
backbone
'resolution' is the definition.
(thesaurus)
'support position of white knight' is the wordplay.
'support' becomes 'back' (to back is to support or endorse).
'position of white knight' becomes 'bone' (I am not sure about this - if you are sure you should believe this answer much more).
'back'+'bone'='BACKBONE'
'in' is the link.
(Other definitions for backbone that I've seen before include "Firmness of character" , "Strength of character" , "Fortitude - protection for the spinal cord" , "Lt protects the spinal cord" , "Spine or courage" .)