Last Supper guest (7)
I believe the answer is:
apostle
'last supper guest' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for apostle that I've seen before include "Early Christian missionary" , "A preacher of gospels" , "Peter, perhaps" , "Vigorous campaigner" , "Luke or John, say" .)