Wild cougar with huge tail and backbone (7)
I believe the answer is:
courage
'backbone' is the definition.
(thesaurus)
'wild cougar with huge tail' is the wordplay.
'wild' indicates an anagram.
'with' is a charade indicator (letters next to each other).
'tail' indicates one should take the final letters.
The final letter of 'huge' is 'e'.
'cougar' with letters rearranged gives 'courag'.
'courag'+'e'='COURAGE'
'and' acts as a link.
(Other definitions for courage that I've seen before include "Bravery, pluck" , "Bravery, heroism" , "Daring" , "Ability to conquer fear or despair" , "See 6" .)