Card sure to shake champion (8)
I believe the answer is:
crusader
'champion' is the definition.
(I've seen this before)
'card sure to shake' is the wordplay.
'to shake' indicates an anagram.
'card'+'sure'='cardsure'
'cardsure' is an anagram of 'CRUSADER'.
(Other definitions for crusader that I've seen before include "Medieval fighter for the Holy Land" , "An old soldier" , "One campaigning vigorously" , "What Simon de Montfort became" , "religious warrior" .)